Make html::{SyntaxHighlight,HighlightMacros} take a const Preprocessor.

This is conceptually correct, but adds a huge hack to HighlightMacros which is
in fact doing all sorts of mutation to the Preprocessor. See FIXME.

Chris, please review.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@86107 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed