Integrate perlio:

[  9267]
More EBCDIC stuff:
- Loose the extra level of function on ASCII.
- spotted a chr(0) issue in sv.c
- re-work of UTF-X tr/// ranges to work in Unicode
space. Still issues with the "0xff is illegal UTF-8" hack.
- Yet another ad. hoc. utf8 'upgrade' in op.c recoded
(why do it once when you can do it all over the place :-(
- Enable HINTS_UTF8 on EBCDIC - then ignore it in toke.c,
need utf8.pm for swashes.
- Simplified and commented scan_const() in toke.c
Still something wrong regexp and tr (swashes?).

p4raw-link: @9267 on //depot/perlio: 2b9d42f0ba1bb562fe21327dc7948ab1a5397a19

p4raw-id: //depot/perl@9268