Don't re-parse the framework resources all the time.

A small optimization to the resource code, to not re-parse the framework
resources every time we build a new AssetManager.  Instead, you can now
construct a ResTable from a previously created one...  of course, like the
existing code for using the data in-place, you can't delete the original
ResTable until you have deleted the one that has been constructed from it.
diff --git a/include/utils/ResourceTypes.h b/include/utils/ResourceTypes.h
index eb4151a..93bca4a 100644
--- a/include/utils/ResourceTypes.h
+++ b/include/utils/ResourceTypes.h
@@ -1580,6 +1580,7 @@
                  bool copyData=false);
     status_t add(Asset* asset, void* cookie,
                  bool copyData=false);
+    status_t add(ResTable* src);
 
     status_t getError() const;