[PATCH] use APR's ctypes on EBCDIC systems

The current svn_ctype_* implementation depends on ASCII character encoding.
APR's ctype functions are portable, so use those on EBCDIC systems.

A somewhat surprising side effect is that svn messages become mostly
readable on z/OS with the help of svn_utf__cstring_from_utf8_fuzzy().

I thought it would be more readable to have one #if around the entire block
of svn_ctype_is* macros rather than around each individual macro. I did not
want to create a second set of nearly duplicate Doxygen docs so I just
punted on those. Let me know if you'd prefer to see it formatted
differently.

Greg

[[[ Use portable ctypes on EBCDIC systems ]]]