CC Mode: correct the calculation and handling of c-use-category.

CC Mode: correct the calculation and handling of c-use-category.

This fixes bug #56629.  The use of c-use-category was inconsistent, with the
result that it would be nil at compilation time, but t at run time.  This
resulted in wrongly writing syntax-table text properties to <s and >s, yet
testing for category properties on them.

* lisp/progmodes/cc-defs.el (c-use-category): Move to after the definition of
c-<-as-paren-syntax and c->-as-paren-syntax so as correctly to be able to use
their values.  Put an eval-when-compile around the calculation of its value,
to reduce the chances of future failure.
(c-mark-<-as-paren, c-mark->-as-paren, c-unmark-<->-as-paren, c-sc-scan-lists)
(c-sc-parse-partial-sexp): Wrap c-use-category in (eval-when-compile ...) as
an optimization, preventing the XEmacs code also being generated.