Win32 PerlIO intermediate state now working as expected.

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-id: //depot/perlio@7802