Previously, we checked tokens for tok::identifier to see if they
were identifiers inside an Objective-C selector.
However, this missed C++ keywords like new and delete.
To fix this, this diff uses getIdentifierInfo() to find
identifiers or keywords inside Objective-C selectors.
Test Plan: New tests added. Ran tests with:
% make -j16 FormatTests && ./tools/clang/unittests/Format/FormatTests