[LLVM-C] Add Section and Symbol Iterator Accessors for Object File Binaries
Summary: This brings us to full feature parity with the old API, so I've deprecated it and updated the tests. I'll do a follow-up patch to do some more cleanup and documentation work in this header.
Reviewers: whitequark, deadalnix
Reviewed By: whitequark
Subscribers: hiraditya, llvm-commits
Differential Revision: https://reviews.llvm.org/D60407