Tweak the canned win32/config.* files

Tweak the canned win32/config.* files

uselargefiles, usemultiplicity, useperlio and useithreads are now
off in the canned win32/config_H.* files, so change these to match.

Also scrap the misleading ~USE_PERLIO~ and ~USE_SITECUST~ tags
which don't actually work since no such CFG_VARS are passed in to
config_sh.PL. (The useperlio and usesitecustomize entries actually
get substituted by the more general "if (/^([\w_]+)=(.*)$/)" case.)

p4raw-id: //depot/perl@25215