Make sure DRI drawables are cleaned up when client dies.

The previous scheme didn't work when the client didn't create the core drawable,
e.g. the root or composite overlay window. Use refcounting via special client
resources to fix that.

GL/glx/glxext.c

@@ -61,6 +61,11 @@ xGLXSingleReply __glXReply;
 */
 static __GLXclientState *__glXClients[MAXCLIENTS + 1];
 
+/*
+** Client that called into GLX dispatch.
+*/
+ClientPtr __pGlxClient;
+
 /*
 ** Forward declarations.
 */
@@ -549,6 +554,8 @@ static int __glXDispatch(ClientPtr client)
 	GLboolean rendering = opcode <= X_GLXRenderLarge;
 	__glXleaveServer(rendering);
 
+	__pGlxClient = client;
+
 	retval = (*proc)(cl, (GLbyte *) stuff);
 
 	__glXenterServer(rendering);