Add MIT license to Makefiles

Signed-off-by: Daira Hopwood <daira@jacaranda.org>

Makefile.am

@@ -1,3 +1,9 @@
+# Copyright (c) 2016-2019 The Zcash developers
+# Copyright (c) 2013-2019 The Bitcoin Core developers
+# Copyright (c) 2013-2019 Bitcoin 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

@@ -1,3 +1,9 @@
+# Copyright (c) 2016-2019 The Zcash developers
+# Copyright (c) 2013-2019 The Bitcoin Core developers
+# Copyright (c) 2013-2019 Bitcoin 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) $(SAN_LDFLAGS) $(HARDENED_LDFLAGS)

src/Makefile.test.include

@@ -1,3 +1,9 @@
+# Copyright (c) 2016-2019 The Zcash developers
+# Copyright (c) 2013-2019 The Bitcoin Core developers
+# Copyright (c) 2013-2019 Bitcoin 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
 noinst_PROGRAMS += test/test_bitcoin
 TEST_SRCDIR = test