Readd Big5: some large databases setup are still requiring it.

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

Remove zh_TW.Big5 locale

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.

Posixify the locales name for variants

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)