The tables have been renamed to _C_ctype_, _C_tolower_, and _C_toupper_
as they are tables for the C locale. When switching to a new locale, the
pointers will be set to point to tables specific to the new locale.
in the text segment. When we implement locales, the isctype macros/functions
will reference this table (or a locale specific table) through a pointer, but
for right now, it continues to reference the _ctype_ table directly.
Standard C requires tolower to return a character that is !isupper unchanged
which was not being done with the macro. The function version does the
right thing, so the loss of the macro is no great deal.
I didn't eliminate the macros entirely, since X/Open's XPG3 requires _tolower
and _toupper with the same semantics. But, like isascii/toascii, they are
removed from the namespace if either ANSI_SOURCE or _POSIX_SOURCE is defined.
