Remove Windows makefile support for building without PerlIO

Remove Windows makefile support for building without PerlIO

As noted in #123394, building without PerlIO was all but deprecated in
5.18.0 and is no longer supported by Configure on POSIX systems, so there
is no need for the Windows makefiles to provide support for it either.

Therefore, we can simply enable PerlIO in the canned configuration files
and remove any fiddling with that setting for the real configuration,
which means that miniperl will also now have PerlIO enabled without
needing the recently added change to win32.h.