Add MIT license to Makefiles

Makefile.am

+# Copyright (c) 2013-2016 The Bitcoin Core developers
+# Distributed under the MIT software license, see the accompanying
+# file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
 ACLOCAL_AMFLAGS = -I build-aux/m4
 SUBDIRS = src
 if ENABLE_MAN

src/Makefile.am

+# Copyright (c) 2013-2016 The Bitcoin Core developers
+# Distributed under the MIT software license, see the accompanying
+# file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
 DIST_SUBDIRS = secp256k1 univalue
 
 AM_LDFLAGS = $(PTHREAD_CFLAGS) $(LIBTOOL_LDFLAGS) $(HARDENED_LDFLAGS)

src/Makefile.bench.include

+# Copyright (c) 2015-2016 The Bitcoin Core developers
+# Distributed under the MIT software license, see the accompanying
+# file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
 bin_PROGRAMS += bench/bench_bitcoin
 BENCH_SRCDIR = bench
 BENCH_BINARY = bench/bench_bitcoin$(EXEEXT)

src/Makefile.leveldb.include

+# Copyright (c) 2016 The Bitcoin Core developers
+# Distributed under the MIT software license, see the accompanying
+# file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
 LIBLEVELDB_INT = leveldb/libleveldb.a
 LIBMEMENV_INT  = leveldb/libmemenv.a
 

src/Makefile.qt.include

+# Copyright (c) 2013-2016 The Bitcoin Core developers
+# Distributed under the MIT software license, see the accompanying
+# file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
 bin_PROGRAMS += qt/bitcoin-qt
 EXTRA_LIBRARIES += qt/libbitcoinqt.a
 

src/Makefile.qttest.include

+# Copyright (c) 2013-2016 The Bitcoin Core developers
+# Distributed under the MIT software license, see the accompanying
+# file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
 bin_PROGRAMS += qt/test/test_bitcoin-qt
 TESTS += qt/test/test_bitcoin-qt
 

src/Makefile.test.include

+# Copyright (c) 2013-2016 The Bitcoin Core developers
+# Distributed under the MIT software license, see the accompanying
+# file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
 TESTS += test/test_bitcoin
 bin_PROGRAMS += test/test_bitcoin
 TEST_SRCDIR = test