bin/45056: sort -f works incorrectly with utf-8 locale

[cheusov%tut.by@localhost]

>Number:         45056
>Category:       bin
>Synopsis:       sort -f works incorrectly with utf-8 locale
>Confidential:   no
>Severity:       serious
>Priority:       low
>Responsible:    bin-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sun Jun 12 11:55:00 +0000 2011
>Originator:     Aleksey Cheusov
>Release:        NetBSD 5.99.52
>Organization:
>Environment:
System: NetBSD asrock.chizhovka.net 5.99.52 NetBSD 5.99.52 (GENERIC) #0: Wed 
Jun 1 01:50:07 UTC 2011 
builds%b7.netbsd.org@localhost:/home/builds/ab/HEAD/amd64/201106010020Z-obj/home/builds/ab/HEAD/src/sys/arch/amd64/compile/GENERIC
 amd64
Architecture: x86_64
Machine: amd64
>Description:
sort -f doesn't work correctly with utf-8 locale.

/usr/pkg/heirloom/bin/posix2001/sort from wip/heirloom-sort
package work correctly.

typescript and input file in utf-8 encoding is available here
ftp://ftp.netbsd.org/pub/NetBSD/misc/cheusov/sort-f_bug/

Input file 2.txt contains [Mm]ather and [Ff]ather written in Russian.
>How-To-Repeat:
See
ftp://ftp.netbsd.org/pub/NetBSD/misc/cheusov/sort-f_bug/typescript
>Fix: