[llvm-nm] Add tapi file support

Summary:
This commit is the final one for adding tapi support to the llvm-nm implementation.
This commit also has accompanying tests the additions to lib/Object

Reviewers: ributzka, steven_wu

Reviewed By: ributzka

Subscribers: hiraditya, plotfi, dexonsmith, rupprecht, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D66160

llvm-svn: 371576