Rewrite all Property related functions in terms of StringRef.
This was a bit tricky, especially for things like
OptionValueArray and OptionValueDictionary since they do some
funky string parsing. Rather than try to re-write line-by-line
I tried to make the StringRef usage idiomatic, even though
it meant often re-writing from scratch large blocks of code
in a different way while keeping true to the original intent.
The finished code is a big improvement though, and often much
shorter than the original code. All tests and unit tests
pass on Windows and Linux.
llvm-svn: 287242