Merge remote-tracking branch 'sonicadvance/OSX-NoX11Support'

I've come around to the various contributors' positions: X11 on OSX is
basically dead, and we're not serving our users by trying to support
it.

configure.ac

@@ -78,7 +78,7 @@ case $host_os in
         ;;
     darwin*)
         build_egl=no
-        build_glx=yes
+        build_glx=no
         build_wgl=no
         build_apple=yes
         has_znow=no

src/dispatch_common.h

@@ -30,7 +30,7 @@
 #define EPOXY_IMPORTEXPORT __declspec(dllexport)
 #elif defined(__APPLE__)
 #define PLATFORM_HAS_EGL 0
-#define PLATFORM_HAS_GLX 1
+#define PLATFORM_HAS_GLX 0
 #define PLATFORM_HAS_WGL 0
 #define EPOXY_IMPORTEXPORT
 #elif defined(ANDROID)