xgl:  Add xgl header changes for rev30 and 31.

Switched EnumerateLayer parameter order, added conditional definition
of xgl function prototypes, and prepended 'xgl' to all function
prototypes. This included fixes for bugs #13173 and #13180.
diff --git a/layers/multi.cpp b/layers/multi.cpp
index b1aa619..55e1bff 100644
--- a/layers/multi.cpp
+++ b/layers/multi.cpp
@@ -96,17 +96,17 @@
 }
 
 XGL_LAYER_EXPORT XGL_RESULT XGLAPI multi1EnumerateLayers(XGL_PHYSICAL_GPU gpu, XGL_SIZE maxLayerCount, XGL_SIZE maxStringSize,
-                                                         XGL_CHAR* const* pOutLayers, XGL_SIZE * pOutLayerCount,
+                                                         XGL_SIZE* pOutLayerCount, XGL_CHAR* const* pOutLayers,
                                                          XGL_VOID* pReserved)
 {
     if (gpu == NULL)
-        return xglEnumerateLayers(gpu, maxLayerCount, maxStringSize, pOutLayers, pOutLayerCount, pReserved);
+        return xglEnumerateLayers(gpu, maxLayerCount, maxStringSize, pOutLayerCount, pOutLayers, pReserved);
 
     XGL_BASE_LAYER_OBJECT* gpuw = (XGL_BASE_LAYER_OBJECT *) gpu;
     XGL_LAYER_DISPATCH_TABLE* pTable = getLayer1Table(gpuw);
 
     printf("At start of multi1 layer xglEnumerateLayers()\n");
-    XGL_RESULT result = pTable->EnumerateLayers((XGL_PHYSICAL_GPU)gpuw->nextObject, maxLayerCount, maxStringSize, pOutLayers, pOutLayerCount, pReserved);
+    XGL_RESULT result = pTable->EnumerateLayers((XGL_PHYSICAL_GPU)gpuw->nextObject, maxLayerCount, maxStringSize, pOutLayerCount, pOutLayers, pReserved);
     printf("Completed multi1 layer xglEnumerateLayers()\n");
     return result;
 }
@@ -196,17 +196,17 @@
 }
 
 XGL_LAYER_EXPORT XGL_RESULT XGLAPI multi2EnumerateLayers(XGL_PHYSICAL_GPU gpu, XGL_SIZE maxLayerCount, XGL_SIZE maxStringSize,
-                                                         XGL_CHAR* const* pOutLayers, XGL_SIZE * pOutLayerCount,
+                                                         XGL_SIZE* pOutLayerCount, XGL_CHAR* const* pOutLayers,
                                                          XGL_VOID* pReserved)
 {
     if (gpu == NULL)
-        return xglEnumerateLayers(gpu, maxLayerCount, maxStringSize, pOutLayers, pOutLayerCount, pReserved);
+        return xglEnumerateLayers(gpu, maxLayerCount, maxStringSize, pOutLayerCount, pOutLayers, pReserved);
 
     XGL_BASE_LAYER_OBJECT* gpuw = (XGL_BASE_LAYER_OBJECT *) gpu;
     XGL_LAYER_DISPATCH_TABLE* pTable = getLayer2Table(gpuw);
 
     printf("At start of multi2 layer xglEnumerateLayers()\n");
-    XGL_RESULT result = pTable->EnumerateLayers((XGL_PHYSICAL_GPU)gpuw->nextObject, maxLayerCount, maxStringSize, pOutLayers, pOutLayerCount, pReserved);
+    XGL_RESULT result = pTable->EnumerateLayers((XGL_PHYSICAL_GPU)gpuw->nextObject, maxLayerCount, maxStringSize, pOutLayerCount, pOutLayers, pReserved);
     printf("Completed multi2 layer xglEnumerateLayers()\n");
     return result;
 }
@@ -237,7 +237,7 @@
 
 /********************************* Common functions ********************************/
 XGL_LAYER_EXPORT XGL_RESULT XGLAPI xglEnumerateLayers(XGL_PHYSICAL_GPU gpu, XGL_SIZE maxLayerCount, XGL_SIZE maxStringSize,
-                                                      XGL_CHAR* const* pOutLayers, XGL_SIZE * pOutLayerCount,
+                                                      XGL_SIZE* pOutLayerCount, XGL_CHAR* const* pOutLayers,
                                                       XGL_VOID* pReserved)
 {
     if (pOutLayerCount == NULL || pOutLayers == NULL || pOutLayers[0] == NULL || pOutLayers[1] == NULL || pReserved == NULL)