perldelta for locale fixes

This is the delta for 68e8f474bc686a86c064b695b9c7400313d7af65,
and b127e37e51c21b0a36755dcd19811be931a03d83.
pp.c: Use correct size for two arrays.

The number of bytes the result of changing the case of a single UTF-8
character is given by UTF8_MAXBYTES_CASE.  In one of these arrays, space
is saved by using the proper #define; in the other there is no change
except on EBCDIC platforms.
perlfunc: Add caveat about string eval containing NV scalar
lib/locale.t: Remove workaround for now fixed #108378
sv.h: Add comment
PATCH: [perl #112208]: Set utf8 flag on $! appropriately

This patch sets the utf8 flag on $! if the error string passes utf8
validity tests and has some bytes with the upper bit set.  (If none
have that bit set, is an ASCII string, and whether or not it is UTF-8 is
irrelevant.)  This is a heuristic that could fail, but as the reference
in the comments points out this is unlikely.

One can reasonably assume that a UTF-8 locale will return a UTF-8
result.  So another approach would be to look at that (but we wouldn't
want to turn the flag on for a purely ASCII string anyway, as that could
change the semantics from existing behavior by making the string follow
Unicode rules, whereas it didn't have to before.)  But we have no sure
way of knowing if we have a UTF-8 locale or not.  The string returned by
setlocale() is defined as opaque, and on WIndows at least it really is.
When a locale has messages outside ASCII, one could pretty reliably
see if it is a UTF-8 locale by examining for UTF-8 validity the return
of strerror() of every possible errno.  This could be done at setlocale
time.  But until the heuristic in this patch is shown to not be good
enough, I don't see the need to do this extra work.
util.c: Avoid unnecessary setlocale() calls

This code sets the locale to C around its work.  This is unnecessary if
the locale is already C, and there is an existing global that indicates
this, that can be tested to avoid the sets.
pp_sys.c: Use macro instead of reinventing it

The Strerror macro is defined properly to handle either case here.
perl.c: Use Strerror instead of strerror

The former works on more systems.
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