Layers initial prototype.

Includes  an auto generated layer (GenericLayer) that wraps  all api calls.
Includes a basic handwritten layer (basicLayer)  that wraps a few apis.
Adds xglGetProcAddr as a new api, which is used to chain layers together.
All layers and loader implement  a dispatch table.
diff --git a/include/xgl.h b/include/xgl.h
index 7fb33cc..7f3986c 100644
--- a/include/xgl.h
+++ b/include/xgl.h
@@ -1761,6 +1761,10 @@
 // ------------------------------------------------------------------------------------------------
 // API functions
 
+void * XGLAPI xglGetProcAddr(
+    XGL_PHYSICAL_GPU gpu,
+    const XGL_CHAR * pName);
+
 // GPU initialization
 
 XGL_RESULT XGLAPI xglInitAndEnumerateGpus(