Downgrade the optimization of regcomp.c on mips and mipsel due to a gcc-4.9 bug

  % cat ~/t.pl
  print ( (q{foo'} =~ /[^']+'/) ?  "ok\n" : "not ok\n" );
  % perl ~/t.pl
  ok
  % ./miniperl ~/t.pl
  not ok

This only happens with -fPIC -ftree-vrp builds.
It is a regression from gcc-4.8.

Bug-Debian: http://bugs.debian.org/754054
Bug: https://rt.perl.org/Ticket/Display.html?id=122817
Patch-Name: fixes/regcomp-mips-optim.diff