New std.uni module

Second attempt to fold it in after review.

Of things new: 
- to{Lower,Upper}InPlace that tries hard to be in-place as far as Unicode allows it.
- std.string versions are aliased to std.uni ones
- better management of tables. Now only the ones that are actually get used are pulled into into the executable (kudos to Rainer!)

Still unknown:
- FreeBSD '-release' bug