Fix various issues with Chinese locales:

- Change short weekday names to use only one Chinese character.
(note: this is a somewhat misunfortunate compromise due to the fact
that some applications are using short buffer for weekday names,
and in ~1905 when 星期 system was created to replace the traditional
七曜 system, which can use 日月火水木金土 to represent Sunday through
Saturday with just one character without any confusion).
- for zh_CN locales: use Arabic numerals for month names, matching the
practice of all other CJK locales
- Regenerate zh_CN.{GB2312,GBK} locales from zh_CN.UTF-8.

Reported by: ygy
Reviewed by: kevlo
MFC after: 2 weeks
Differential Revision: https://reviews.freebsd.org/D18689

Fix ko_KR, zh_CN, zh_HK, and zh_TW locales. r304045 did not fully revert
date/time formats for these locales.

Set date and time formats back to what they were before CLDR

While CLDR brings us a good and up to date source data to generate locales for
all databses we are using for locales, it is not the case of LC_TIME. Where it
does not defines the informations we need.

Put back all the date and time formats from the old locales.
Make it statically for now (in order to be able to merge it now into
11.0-RELEASE). The generation tools will be updated soon.

That gives us time to properly work on LC_TIME during the 12 timeframe.

While here fix abbreviated month for af_ZA (which are already fixed in CLDR
data upstream)

In locales where AP/PM was not defined before CLDR data, remove again the AP/PM
informations

For locales where AP/PM was defined before CLDR data, keep the CLDR information
which was properly translated.

MFC after: 3 days

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)