Integrate perlio:

[ 14595]
Extract something from yesterdays effort - convert my mail on pad
data structures (incoporating Sarathy's corrections/clarifications)
into POD in cv.h which gets autodoc.pl'ed into pod/perlintern.pod.

p4raw-link: @14595 on //depot/perlio: a4f1a0295dfc0733a51ca0623d486d082d04773a

p4raw-id: //depot/perl@14599