Integrate perlio:

[ 14196]
Install dummy signal() handlers for Win32's SIGINT and SIGBREAK
as C runtime seems to get its hands on them even though we said
they were handled.
Still an issue with "die" out of signal handler - get panic: pp_iter

p4raw-link: @14196 on //depot/perlio: f646a69a049030ff75ef540aa2c16835b7972cc1

p4raw-id: //depot/perl@14197