New std.uni meets std.regex

!DO NOT PULL YET!

I've been preparing this for over half a year now.
Puts our std.regex on the new rails of recently revamped std.uni that now it has enough of mojo to power a Unicode-aware regular expression engine. All of it with a minor exception via normal "user-land" public API.

1. 8KLOCs of red speak for themselves. This is a massive code reuse going on.
2. Must yield a faster regex (something to rigorously test, I expect around ~10-20% overall)
3. May fix some Unicode set operation bugs.

TODOs:

1. Regressed ctRegex - it outs of memory on some patterns that previously were passing just fine. In particular blocks 2 & 3 of CT-tests on win32.
2. May have regressed regex compilation speed due to less straight-forward construction.