Integrate perlio:
Jarkko Hietaniemi [Wed, 20 Jun 2001 13:07:49 +0000 (13:07 +0000)]
[ 10747]
Fix PERLIO=unix bug, while restoring maximal buffer in PerlIOBuf_unread.

p4raw-link: @10747 on //depot/perlio: 0c20e1bff223cc739a8992304cad35e8a6d79050

p4raw-id: //depot/perl@10749


Trivial merge