[LLVM-C] Allow Access to the Type of a Binary

Summary: Add an accessor for the type of a binary file.

Reviewers: whitequark, deadalnix

Reviewed By: whitequark

Subscribers: hiraditya, aheejin, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D60366

llvm-svn: 357872