More C.pm tweaks

More C.pm tweaks
  Save globs even if we have saved cv itself before - may be imported.

  While we don't save "bootstrap" CV we need to provide a stub,
  so that if we require it later we don't fall through and attempt
  to DynaLoad module again.

  Attempt to save %INC so that "require" does not reload things
  we have compiled-in (does not work right yet - seems to be due
  to PL_incgv being created in perl_parse() current scheme setting
  GvHV() is "better" than saving the glob, but still does not
  work as I expect).

p4raw-id: //depot/perl@2378