Change release target to run distcheck instead of dist

With distcheck we not only build the distribution files, but also runs
test suite and verifies that the resulting dist file(s) can be built.

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>

Makefile.am

@@ -34,7 +34,7 @@ release-hook:
 	fi
 
 ## Target to run when building a release
-release: dist release-hook md5-dist
+release: distcheck release-hook md5-dist
 	@for file in $(DIST_ARCHIVES); do						\
 		printf "$$file    \tDistribution tarball\n";				\
 		printf "$$file.md5\t"; cat $$file.md5 | cut -f1 -d' ';			\