In addition to standard code separation, this change opens the door
to fixing several include inter-dependencies.

For Qt builds, the build.h file is moved to build/build.h. For regular
builds, it is moved to obj/build.h. This allows the Qt build to be done
in a different directory than the source, and without interfering with
other builds.

All client version information is moved to version.cpp, which optionally
(-DHAVE_BUILD_INFO) includes build.h. build.h is automatically generated
on supporting platforms via contrib/genbuild.sh, using git describe.

The git export-subst attribute is used to put the commit id statically
in version.cpp inside generated archives, and this value is used if no
build.h is present.

The gitian descriptors are modified to use git archive instead of a
copy, to create the src/ directory in the output. This way,
src/src/version.cpp will contain the static commit id. To prevent
gitian builds from getting the "-dirty" marker in their git-describe
generated identifiers, no touching of files or running sed on the
makefile is performed anymore. This does not seem to influence
determinism.

Design goals:
 * Only keep a limited number of addresses around, so that addr.dat does not grow without bound.
 * Keep the address tables in-memory, and occasionally write the table to addr.dat.
 * Make sure no (localized) attacker can fill the entire table with his nodes/addresses.

See comments in addrman.h for more detailed information.

This turns on most gcc warnings, and removes some unused variables and other code that triggers warnings.
Exceptions are:
 -Wno-sign-compare : triggered by lots of comparisons of signed integer to foo.size(), which is unsigned.
 -Wno-char-subscripts : triggered by the convert-to-hex functions (I may fix this in a future commit).

This introduces CNetAddr and CService, respectively wrapping an
(IPv6) IP address and an IP+port combination. This functionality used
to be part of CAddress, which also contains network flags and
connection attempt information. These extra fields are however not
always necessary.

These classes, along with logic for creating connections and doing
name lookups, are moved to netbase.{h,cpp}, which does not depend on
headers.h.

Furthermore, CNetAddr is mostly IPv6-ready, though IPv6
functionality is not yet enabled for the application itself.

Introduces two new RPC calls:
* dumpprivkey: retrieve the private key corresponding to an address
* importprivkey: add a private key to your wallet

The private key format is analoguous to the address format. It is
a 51-character base58-encoded string, that includes a version number
and a checksum.

Includes patch by mhanne:
* add optional account parameter for importprivkey, if omitted use default

Add support to makefile.unix for the same parameters used by bitcoin-qt.pro, dynamic linking unless STATIC=1 is passed

Makefiles now build bitcoind only.
qmake/make in top-level directory is used to build Bitcoin QT
Deleted almost all #ifdef GUI from the code (left one possibly controversial one)
Deleted xpm/ files.

Move CMessageHeader from net.h to protocol.[ch]pp, with the
implementation in the .cpp compilation unit (compiling once is enough).

This commit does *not* and should not modify *any* code, it only moves
it from net.h and splits it across protocol.cpp and protocol.hpp.

Indentation changes aside the closest thing to a modification of code is
the addition of the 'TODO' comment (the execution of which requires code
modifications and thus doesn't belong in this commit).
Signed-off-by: Giel van Schijndel <me@mortis.eu>

Signed-off-by: Giel van Schijndel <me@mortis.eu>

Spotted by Venkatesh Srinivas <me@endeavour.zapto.org>

There were some problems with the existing testing setup:

 - Makefile rules for test-file compilation used CFLAGS instead of
   CXXFLAGS in makefile.unix

This commit adds support for ckeys, or enCrypted private keys, to the wallet.
All keys are stored in memory in their encrypted form and thus the passphrase
is required from the user to spend coins, or to create new addresses.

Keys are encrypted with AES-256-CBC using OpenSSL's EVP library. The key is
calculated via EVP_BytesToKey using SHA512 with (by default) 25000 rounds and
a random salt.

By default, the user's wallet remains unencrypted until they call the RPC
command encryptwallet <passphrase> or, from the GUI menu, Options->
Encrypt Wallet.

When the user is attempting to call RPC functions which require the password
to unlock the wallet, an error will be returned unless they call
walletpassphrase <passphrase> <time to keep key in memory> first.

A keypoolrefill command has been added which tops up the users keypool
(requiring the passphrase via walletpassphrase first).
keypoolsize has been added to the output of getinfo to show the user the
number of keys left before they need to specify their passphrase (and call
keypoolrefill).

Note that walletpassphrase will automatically fill keypool in a separate
thread which it spawns when the passphrase is set. This could cause some
delays in other threads waiting for locks on the wallet passphrase, including
one which could cause the passphrase to be stored longer than expected,
however it will not allow the passphrase to be used longer than expected as
ThreadCleanWalletPassphrase will attempt to get a lock on the key as soon
as the specified lock time has arrived.

When the keypool runs out (and wallet is locked) GetOrReuseKeyFromPool
returns vchDefaultKey, meaning miners may start to generate many blocks to
vchDefaultKey instead of a new key each time.

A walletpassphrasechange <oldpassphrase> <newpassphrase> has been added to
allow the user to change their password via RPC.

Whenever keying material (unencrypted private keys, the user's passphrase,
the wallet's AES key) is stored unencrypted in memory, any reasonable attempt
is made to mlock/VirtualLock that memory before storing the keying material.
This is not true in several (commented) cases where mlock/VirtualLocking the
memory is not possible.

Although encryption of private keys in memory can be very useful on desktop
systems (as some small amount of protection against stupid viruses), on an
RPC server, the password is entered fairly insecurely. Thus, the only main
advantage encryption has for RPC servers is for RPC servers that do not spend
coins, except in rare cases, eg. a webserver of a merchant which only receives
payment except for cases of manual intervention.

Thanks to jgarzik for the original patch and sipa, gmaxwell and many others
for all their input.

Conflicts:

	src/wallet.cpp

This reverts commit ee1f8842.

Stupid, stupid me...there is exactly 0 way to convince make to
execute a conditional based on a target-specific variable.

This is a bit of an ugly hack, but its the only way to do it.

make -f makefile.{unix,osx,mingw} test_bitcoin
to compile dumb, do-almost-nothing placeholder unit tests.

This introduces two new source files, keystore.cpp and wallet.cpp with
corresponding headers. Code is moved from main and db, in a preparation
for a follow-up commit which introduces the classes CWallet and CKeyStore.

there is no internal modification of any file in this commit

files are moved into directories according to established standards in
sourcecode distribution; these directories contain:

 src - Files that are used in constructing the executable binaries,
       but are not installed.

 doc - Files in HTML and text format that document usage, quirks of
       the implementation, and contributor checklists.

 locale - Files that contain human language translation of strings
          used in the program

 contrib - Files contributed from distributions or other third party
 	   implementing scripts and auxiliary programs

Fixes link failure when using the 'gold' linker.