layers: Update GetExtensionSupport() to handle queries for layer name

Layers now support loader querying their layer name via GetExtensionSupport
in addition to EnumerateLayers.
Also fixed bugs in ObjectTracker and DrawState to add the extensions they
support in the GetExtensionSupport queries.

Conflicts:
	xgl-layer-generate.py
diff --git a/layers/draw_state.cpp b/layers/draw_state.cpp
index c239119..503c08a 100644
--- a/layers/draw_state.cpp
+++ b/layers/draw_state.cpp
@@ -1514,6 +1514,25 @@
     return result;
 }
 
+XGL_LAYER_EXPORT XGL_RESULT XGLAPI xglGetExtensionSupport(XGL_PHYSICAL_GPU gpu, const char* pExtName)
+{
+    XGL_BASE_LAYER_OBJECT* gpuw = (XGL_BASE_LAYER_OBJECT *) gpu;
+    XGL_RESULT result;
+    /* This entrypoint is NOT going to init its own dispatch table since loader calls here early */
+    if (!strcmp(pExtName, "DrawState") || !strcmp(pExtName, "drawStateDumpDotFile") ||
+        !strcmp(pExtName, "drawStateDumpCommandBufferDotFile") || !strcmp(pExtName, "drawStateDumpPngFile"))
+    {
+        result = XGL_SUCCESS;
+    } else if (nextTable.GetExtensionSupport != NULL)
+    {
+        result = nextTable.GetExtensionSupport((XGL_PHYSICAL_GPU)gpuw->nextObject, pExtName);
+    } else
+    {
+        result = XGL_ERROR_INVALID_EXTENSION;
+    }
+    return result;
+}
+
 XGL_LAYER_EXPORT XGL_RESULT XGLAPI xglEnumerateLayers(XGL_PHYSICAL_GPU gpu, size_t maxLayerCount, size_t maxStringSize, size_t* pOutLayerCount, char* const* pOutLayers, void* pReserved)
 {
     if (gpu != NULL)
@@ -2741,6 +2760,8 @@
         return (void*) xglCreateDevice;
     if (!strcmp(funcName, "xglDestroyDevice"))
         return (void*) xglDestroyDevice;
+    if (!strcmp(funcName, "xglGetExtensionSupport"))
+        return (void*) xglGetExtensionSupport;
     if (!strcmp(funcName, "xglEnumerateLayers"))
         return (void*) xglEnumerateLayers;
     if (!strcmp(funcName, "xglQueueSubmit"))