Comment parsing: add more tests for html character references


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@172923 91177308-0d34-0410-b5e6-96231b3b80d8
Use llvm::hexDigitValue in comment lexer


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@172924 91177308-0d34-0410-b5e6-96231b3b80d8
Actually update the test, fixup for r172923


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@172925 91177308-0d34-0410-b5e6-96231b3b80d8