Integrate perlio:

[ 16657]
Fix the crlf.t buffer leak
- actually a generic PerlIOBuf_xxx derived leak-on-pop, but :crlf
flagged it because it is more often popped without stream
being closed.
- Define non-noop PerlIOBuf_popped(), use it and export it.
p4raw-link: @16657 on //depot/perlio: 44798d05173226aecbb6247375cc88a9dd809540

p4raw-id: //depot/perl@16661