Some Win32 Config fixes for patchlevel and perl_patchlevel:

Some Win32 Config fixes for patchlevel and perl_patchlevel:
- Set $Config{patchlevel} to PERL_VERSION (it was previously blank
  because it was wrongly being set from PATCHLEVEL, which was blank)
- Set $Config{perl_patchlevel} and $Config{PERL_PATCHLEVEL} to the
  value in the top-level ".patch" file if it exists (the former was
  previously not set, while the latter was previously wrongly set to
  PERL_VERSION)

p4raw-id: //depot/perl@31569