Fix selectors not being objc-uniquified in the expression parser after a recent renaming in clang (clang change for revision 221451). This broke all objective C expressions in LLDB.

git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@221632 91177308-0d34-0410-b5e6-96231b3b80d8
Fix comments to match the current reality.

git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@221633 91177308-0d34-0410-b5e6-96231b3b80d8