1.0.39.8: Inline-compare more character codes on SB-UNICODE PPC.

1.0.39.8: Inline-compare more character codes on SB-UNICODE PPC.

  * In 1.0.38.5, I disabled the -c character compare VOPs on SB-UNICODE
because the instruction used (cmplwi) was limited to a 16-bit constant.

  * Added a predicate to determine if a character can safely be used in
the -c character compare VOPs.

  * Changed the required constant type on the -c character compare VOPs
from CHARACTER to (SATISFIES <the-new-predicate>).

  * Back in the commit comment for 1.0.38.5 I said that there was no
good way to conditionally use the VOPs.  Looks like I was wrong, unless
you want to argue that SATISFIES types are bad.