Removed direct dependency on OpenGL (call current_video->glGetString() instead

 of glGetString() directly)...otherwise we'd have to explicitly link to a
 libGL.  --ryan.

--HG--
extra : convert_revision : svn%3Ac70aab31-4412-0410-b14c-859654838e24/trunk%40644

src/video/x11/SDL_x11gl.c

@@ -240,7 +240,7 @@ static int ExtensionSupported(const char *extension, const char *all_extensions)
 	if (where || *extension == '\0')
 	      return 0;
 	
-	extensions = glGetString(GL_EXTENSIONS);
+	extensions = current_video->glGetString(GL_EXTENSIONS);
 	/* It takes a bit of care to be fool-proof about parsing the
 	 *      OpenGL extensions string. Don't be fooled by sub-strings,
 	 *           etc. */