ICU incorporation and string changes heads-up

[Jeff Clites]

I'm almost finished preparing a patch which incorporates the usage of 
ICU, and makes some additional changes to the internal representation 
of strings. These changes give us an internal representation model 
which is a bit simpler, and is measurably faster. (More details to 
follow with the actual patch, of course.)

The patch itself is shaping out to be rather large (mostly because I've 
added an interpreter argument to the string functions which were 
lacking it, and updated the places where these function are called), 
but is self-contained in the sense that (1) the functions which 
actually call out directly to any ICU API are collected into one file 
(for clarity, and in case we ever want to transition to a different 
library), (2) there are minimal API changes, and (3) the GC behavior of 
strings isn't affected.

It will take me a few more days to finish this up, but I wanted to give 
everyone a heads-up that this is on the way.

JEff