Speed up string decomposition.

Reduce consing.
Recursively expand canonical decompositions at build time.
More character normalization speed ups.

Sort combiners while doing decompose-string.
Now normalizing a string is actually faster than calling
QUICK-NORMALIZATION-CHECK, so, stop doing it.
Remove NIL from *bidi-mirroring-glyphs*.

Properly parse BidiMirroring.txt
Remove FIXME that seems to refer to nothing in particular.
Update the documentation and tests to account for the removal of the UNICODE1_ prefix on UNICODE 1 names.