Fix direct calls to __wrap_sym when it is relocated.

Patch by Matthew Koontz!

Before, direct calls to __wrap_sym would not map to valid PLT entries,
so they would crash at runtime. This change maps such calls to the same
PLT entry as calls to sym that are then wrapped.

Differential Revision: https://reviews.llvm.org/D48502

llvm-svn: 336609