[PATCH] [prototype] Adding line table debug information to LLVM on Windows

[Timur Iskhodzhanov]

2013/12/20 dblaikie at gmail.com <dblaikie at gmail.com>:
> If you don't need null values, you could have <null, ""> be the empty key
> and <"", null> be the tombstone, or something like that.

Or I can use an explicit second DenseMap template parameter... will
give it a try.

Would appreciate if you continue to review the rest of the patch
assuming I'll fix this header soon :)