Wide strings and the VM

[Mike Gran]

Hi-

I wonder if I could get someone to check out what I've done with wide
strings and the VM on the string_abstraction2 branch with commit
efb042...

That code is quite confusing, and I may have made a mess of it.  And, I
wasn't sure about alignment.

I daresay that this Unicode string stuff is now a genuine alpha.  It is
feature complete: wide chars, wide strings and symbols, Unicode-capable
SRFI-14, and VM / compiler updates.

Unicode capable regex will, unfortunately, have to wait until
libunistring finishes their implementation.

Still have old ideas from Andy to incorporate, though.  More testing, of
course.  And some speed improvements are probably necessary.

--Mike