A small set of modifications to allow external applications to use the RUNTIME API

This is a set of modification made from the look at the exageostat application that not only uses chameleon algorithms, but also tries to add its own algorithms using the RUNTIME API from chameleon. These changes are made to avoid conflict and copy/paste in ExaGeostat.

include/chameleon.h

@@ -30,7 +30,6 @@
  * CHAMELEON types and constants
  */
 #include "chameleon/config.h"
-#define _GNU_SOURCE 1
 #include <stdio.h>
 #include "chameleon/constants.h"
 #include "chameleon/types.h"