gallium: Disable memory debugging for Windows OGL.

Unfortunately both Mesa and Gallium use the same defines for memory
allocation (MALLOC, FREE, etc), and worse, some times memory is allocated
with one set and freed with the other set, causing the homegrown memory
debugger to trip on itself.

In the future mesa and gallium should use different names, but for now,
memory debugging on Windows will have to be carried with different tools..

src/gallium/auxiliary/util/u_memory.h

@@ -52,7 +52,7 @@ extern "C" {
 #endif
 
 
-#if defined(PIPE_OS_WINDOWS) && defined(DEBUG) 
+#if defined(PIPE_SUBSYSTEM_WINDOWS_DISPLAY) && defined(DEBUG) 
 
 /* memory debugging */