Fix Autotools failure requiring README (oops)

Automake requires README to exist by default, but it was renamed to
README.rst recently.  Thus, change Automake strictness to `foreign'
for README to be optional, and distribute README.rst explicitly.

Although `foreign' strictness don't require any of the README, INSTALL,
COPYING, etc. files, it still includes them if available, so the
distribution still includes them.

Makefile.am

@@ -36,6 +36,7 @@ EXTRA_DIST = \
 	geany.gladep \
 	ChangeLog.pre-0-17 \
 	HACKING \
+	README.rst \
 	README.I18N \
 	README.Packagers \
 	po/intl_stats.sh \

configure.ac

@@ -6,7 +6,7 @@ AC_INIT([Geany], [1.22],
 AC_CONFIG_SRCDIR([src/geany.h])
 AC_CONFIG_AUX_DIR([build-aux])
 AC_CONFIG_MACRO_DIR([m4])
-AM_INIT_AUTOMAKE
+AM_INIT_AUTOMAKE([foreign])
 AC_CONFIG_HEADERS([config.h])
 
 m4_ifdef([AM_SILENT_RULES],[AM_SILENT_RULES([yes])])