pkg/42620: irssi patch for using threaded perl 5.10 breaks build with (threaded) 5.8

[duck%shangtai.net@localhost]

>Number:         42620
>Category:       pkg
>Synopsis:       irssi patch for using threaded perl 5.10 breaks build with 
>(threaded) 5.8
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    pkg-manager
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Fri Jan 15 05:05:00 +0000 2010
>Originator:     duck%shangtai.net@localhost
>Release:        NetBSD 4.0_STABLE
>Organization:
>Environment:
System: NetBSD knightrider.shangtai.net 4.0_STABLE NetBSD 4.0_STABLE 
(KITT.nb4.0) #1: Wed Dec 3 17:25:11 EET 2008 
duck%knightrider.shangtai.net@localhost:/usr/obj/sys/arch/alpha/compile.alpha/KITT.nb4.0
 alpha
Architecture: alpha
Machine: alpha
>Description:
irssi doesn't build with the fix for threaded perl 5.10 applied (patch-ad) when 
the perl package installed is perl-5.8.8nb7; PERLIO_INIT isn't defined.

>How-To-Repeat:
Attempt to build irssi with perl 5.8
>Fix:
Somehow conditionally apply patch-ad only when we're using threaded perl 5.10?