Fix autogen.sh errors

Based on original patch from Dan Frincu <df.cluster@gmail.com>

Signed-off-by: Jan Friesse <jfriesse@redhat.com>
Reviewed-by: Fabio M. Di Nitto <fdinitto@redhat.com>

configure.ac

@@ -167,7 +167,7 @@ LIB_MSG_RESULT(m4_shift(m4_shift($@)))dnl
 cc_supports_flag() {
 	local CFLAGS="$@"
 	AC_MSG_CHECKING([whether $CC supports "$@"])
-	AC_COMPILE_IFELSE([int main(){return 0;}] ,
+	AC_COMPILE_IFELSE([AC_LANG_SOURCE([int main(){return 0;}])] ,
 			  [RC=0; AC_MSG_RESULT([yes])],
 			  [RC=1; AC_MSG_RESULT([no])])
 	return $RC