Integrate perlio:

[  7802]
Win32 PerlIO intermediate state now working as expected.
- In current state we are still using C runtime in text/binary
mode and "crlf" layer is just a dummy (clone of perlio buffer layer).
- PERLIO=stdio and PERLIO=unix pass all expected tests.
- PERLIO=perlio fails t/lib/dprof.t because Dprof.xs calls PerlIO_tell()
and PerlIO_seek() and the dummy crlf layer is not making adjustments
for CRLF translation happening in C runtime. All other tests pass.
Added note to README.win32 to point out the snags of doing a perl build
with Norton AntiVirus turned on.
Tweaked t/pragma/warnings.t so that when run stand-alone you can tell
which file a fail comes from.
Updated "canned" config.h to match the one generated.

p4raw-link: @7802 on //depot/perlio: 3789aae2a16ba33c51e31b2ff3418eaef6c2ff4d

p4raw-id: //depot/perl@7819