Cleaning up some range-based for loops so that the automatic type deduction is more explicit about pointers and const. Did some minor drive-by const correctness fixes and identifier updates as well. No functional changes.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@209233 91177308-0d34-0410-b5e6-96231b3b80d8