Integrate perlio:

[ 13848]
The CR at EOF fix earlier broke CR at end-of-buffer.
This should be okay for both?

[ 13847]
Correct checking code which Ilya spotted was tripped by CR at EOF.
Also tone down perl -DP tracing of sv_gets.

[ 13846]
Fix mis-parse of autoloaded usage code by declaring the sub

p4raw-link: @13848 on //depot/perlio: a0d1d361c93b39102154ecff3ddb8a1be74034b8
p4raw-link: @13847 on //depot/perlio: ba7abf9d1538e18db741ea51e49e01e9ac1ea8a2
p4raw-link: @13846 on //depot/perlio: f2b27c0ebcd845b38b64790a1a1a6ac3dbdb148e

p4raw-id: //depot/perl@13849