Added raw bitmap access support to GTK 2.0.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@31996 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/rawbmp.h

@@ -160,6 +160,11 @@ typedef wxPixelFormat<unsigned char, 24, 0, 1, 2> wxImagePixelFormat;
     // Cocoa is standard RGB or RGBA (normally it is RGBA)
     typedef wxPixelFormat<unsigned char, 24, 0, 1, 2> wxNativePixelFormat;
 
+    #define wxPIXEL_FORMAT_ALPHA 3
+#elif defined(__WXGTK__)
+    // Under GTK+ 2.X we use GdkPixbuf, which should be RGBA
+    typedef wxPixelFormat<unsigned char, 24, 0, 1, 2> wxNativePixelFormat;
+
     #define wxPIXEL_FORMAT_ALPHA 3
 #endif