Refactor is(SPACE|PSXSP)_(uni|utf8) macros and utf8.c

Refactor is(SPACE|PSXSP)_(uni|utf8) macros and utf8.c

This refactors the isSPACE_uni, is_SPACE_utf8, isPSXSPC_uni,
and is_PSXSPC_utf8 macros in handy.h, so that no function call need be
done to handle above Latin1 input.  These macros are quite small, and
unlikely to grow over time, as Unicode has mostly finished adding white
space equivalents to the Standard.  The functions that implement these
in utf8.c are also changed to use the macros instead of generating a
swash.  This should speed things up slightly, with less memory used over
time as the swash fills.