regexec.c: Use SPACE macros instead of swash

regexec.c: Use SPACE macros instead of swash

This will avoid loading a swash when an above Latin1 code point is
tested to see if it matches \s.  The SPACE macro is quite small, and
unlikely to grow over time, as Unicode has mostly finished adding white
space equivalents to the Standard.

The CCC_TRY_U macro in regexec.c could not be used for this, and I just
expanded out what it would generate, modified to use the macro instead
of a swash.