Remove /^\s*#[#!]?\s*\$FreeBSD\$.*$\n/

Similar commit in main:
(cherry picked from commit d0b2dbfa0ecf)

PR:		228587
Submitted by:	Micil <micheal.maclochlainn@oegaillimh.ie> (LC_TIME)
Reviewed by:	bapt
Approved by:	kib (mentor, implicit)
MFC after:	3 days
Differential revision:	https://reviews.freebsd.org/D17997

MFC after:	2 weeks
Relnotes:	yes

Reported by:	"張君天(Chun-Tien Chang)" <tcs@kitty.2y.idv.tw>

After discussion with many Taiwanese, in IT or not. Big5 is not used anymore.
It is not able to represent lots of the characters used in the language.

MFC after:	1 month
Relnotes:	yes

For all locales with variants:
- if no ambiguity on the locale (only one variant) just use the regular name
- if ambiguity, pick one as default and append @<variant> to the others
  respecting POSIX

As a result:
- All the 3 components locales added recently are renamed to the usual 2
  components version for all but sr_RS.UTF-8
- Set sr_RS.UTF-8 to the cyrillic variant
- Add sr_RS.UTF-8@latin
- Remove the symlinks aliases they were created to represent the 2 components
  version as aliasas and are now useless
- Update the OptionalObsoleteFiles.inc and ObsoleteFiles.inc to reflect those
  changes

Discussed with:	ache@
Approved by:	re@ (gjb)

Serbian locales have triple components to represent the 2 variations of the
locale: Latin and Cyrillic. Previously the tools generatic the locale were
appending both definitions instead of differentiating them.

Reported by:	ache
Approved by:	re (gjb)