Merge branch 'fix_vasprintf' into 'master'

fix undefined vasprintf

See merge request !410

include/chameleon.h

@@ -28,6 +28,7 @@
  * CHAMELEON types and constants
  */
 #include "chameleon/config.h"
+#define _GNU_SOURCE 1
 #include <stdio.h>
 #include "chameleon/constants.h"
 #include "chameleon/types.h"