Custom escape mappings

Right now, \\[nrt] are effectively mapped to space, and some patterns are mapped to '.

Thoughts

The C escaped whitespace frequently trip on Windows paths. It would be possible to move them out of the engine entirely and have projects use patterns.txt instead as needed. Possibly aided by something to automatically suggest it.
Something which can automatically decide html escapes would handle most of the rest. I'm not sure I like this, since I'm not sure I'd always want to run it.
It'd be possible to define a special file with something like:

/&quot;/ => "
/&apos;/ => '

I'm not sure I like this at all as the parsing will be painful.

I could use JSON, but, I don't think that really improves things.