having multiple bindings from all the possible decls which
conceptually map to the same global).
- This eliminates CodeGen depending on the LLVM module for name
lookup.
- This also eliminates the need for ReplaceMapValuesWith (hurrah).
- This handles lookups for FunctionDecls correctly in the presence of
aliases, this was previously broken.
- WIP: Can still clean up & unify variable and function emission.
llvm-svn: 54382