[C++11] Change the interface of getCOFF{Section,Relocation,Symbol} to make it work with range-based for loops.

Reviewers: ruiu

Reviewed By: ruiu

CC: llvm-commits

Differential Revision: http://llvm-reviews.chandlerc.com/D3097

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@204120 91177308-0d34-0410-b5e6-96231b3b80d8