Make multisampling work on mac -- to the first approximation.

git-svn-id: http://root.cern.ch/svn/root/trunk@36706 27541ba8-7e3a-0410-8455-c3a389f83636

graf3d/gl/inc/TGLWSIncludes.h

@@ -16,10 +16,13 @@
 
 #include "TGLIncludes.h"
 
-#ifdef WIN32
-#include <GL/wglew.h>
+#if defined(WIN32)
+#  include <GL/wglew.h>
 #else
-#include <GL/glxew.h>
+#  if defined(__APPLE__)
+#    define GLEW_APPLE_GLX
+#  endif
+#  include <GL/glxew.h>
 #endif
 
 #endif

graf3d/glew/src/glew.c

@@ -29,8 +29,17 @@
 ** THE POSSIBILITY OF SUCH DAMAGE.
 */
+/* ROOT additions begin */
+
 #define GLEW_BUILD
+#if defined(__APPLE__)
+#  define GLEW_APPLE_GLX
+#endif
+
+/* ROOT additions end */
+
+
 #include <GL/glew.h>
 #if defined(_WIN32)