memcheck: Add a 'make memcheck' target that runs valgrind

Checks for memory errors and leaks

https://bugzilla.gnome.org/show_bug.cgi?id=711744

configure.ac

@@ -65,6 +65,7 @@ cflags_set=${CFLAGS+set}
 
 AM_INIT_AUTOMAKE([1.11 -Wno-portability no-define no-dist-gzip dist-xz tar-ustar])
 AM_MAINTAINER_MODE([enable])
+AM_EXTRA_RECURSIVE_TARGETS([memcheck])
 
 # Support silent build rules. Disable
 # by either passing --disable-silent-rules to configure or passing V=1