[PATCH] mscoree: Implement VTable fixup for x86_64 architecture.

[Vincent Povirk]

> 3. It looks like ReallyFixupVTableEntry has potential thread safety
> issue. I mean the case when multiple vtable entries are present within
> one fixup. I could possibly fix that but I think should be an extremely
> rare case to occur, as application should start calling methods in
> parallel right from start of module usage at the first place. So I am
> not sure if it worth doing it.

What's the issue? It should be OK for multiple threads to run it at once.