Laoutlib_creator: keep original of delegate methods.

For specific methods, Layoublib_create can rewrite the implementation
of a method to invoke a delegate instead of the original code. This
allows layoutlib to implement native code or override existing behavior.

This patch also 'saves' the original implementation of a rewritten
method so that the delegate can access the original implementation
as needed. Obviously this is only done for non-native methods.

Given a non-native SomeClass.MethodName, we generate 2 methods:
- A copy of the original method named "SomeClass.MethodName_original".
  The content is the original method as-is from the reader.
- A brand new implementation of SomeClass.MethodName which calls to a
  non-existing method named "SomeClass_delegate.MethodName".
  The implementation of this 'delegate' method is done in layoutlib_brigde.

Change-Id: I5ca2cd3ac55991a8e8a51c417e75ee447bf9e9e6