Use gettext's contexts and extracted comments instead of our pipe syntax

[nbachiyski]

Our current (#3687) functionality for disambiguating and adding descriptions to translated strings has some flaws:

• We are using the same syntax (the pipe) for both disambiguating and adding descriptions
• It screws translation memories, because Approved|main page and Approved|adjective are different strings for them
• Translations get confused and often don't get that the text after | is a description or context

Instead, the recent gettext versions provide the following functionality:

• Contexts, which are part of the PO syntax:

  msgctxt "context"
  msgid "term"
  msgstr "translation"
  

xgettext supports it and most translation tools too. poEdit works correctly with them, but still doesn't show the context anywhere.

• Extracted comments. If there is a comment directly preceding the gettext call, starting with, let's say translators, it is inserted as a comment in the PO file.

  /* translators, see http://php.net/date */
  $date = date(__('d.m.Y'));
  

becomes:

#. translators, see http://php.net/date
msgid "d.m.Y"
msgstr ""

These comments are shown by all translation software.

There is already support for this in the POT generating tools in  http://svn.automattic.com/wordpress-i18n/tools/trunk/

And functions to handle pgettext() and npgettext()?

The current php-gettext library doesn't support contexts. I've got a rewritten, slightly more abstracted, cleaner and having some tests gettext library at  http://svn.glotpress.org/trunk/pomo/

I will send a patch soon.

Here is a patch, which switches from current php-gettext to the GlotPress one. It expects the new library files to be in wp-includes/pomo. In the beginning we can add it as an external and then we can trim it just to the needed files.

wp-includes/gettext.php and wp-includes/streams.php aren't needed any more.

I named the new context functions _x and _nx. It resembles conteXt.

Note: the patch includes the deprecation part from #9111.

(In [10584]) Switch to pomo lib. Support gettext contexts. Deprecate long form functions. Props nbachiyski. fixes #9112 #9111

Went ahead and added pomo as a real directory instead of an external since switching from an external to a directory always seems to cause grief. We'll just have to keep it in sync.

First patch using _x and extracted coments

Here is the first patch, which adds some _x() calls and uses extracted comments like translators: instead of _c().

(In [10680]) Use _x() and extracted comments. Props nbachiyski. see #9112

Next round of _x and comments. Role names caused some trouble, because they are kept in DB and currently their values have the |Role name suffix.

(In [10767]) gettext contexts. Props nbachiyski. see #9112

The last patch of the series, a little bit larger than the previous ones.

Fixes several other minor problems:

• adds a lot of translator comments
• noop functions don't need to have similar interface to the standard gettext functions, so I got rid of the dummy args
• feed_links had separator spelled as seperator and a typo in one of the indices
• _x didn't have a dummy entry in the script/style loadign scrits

(In [10774]) gettext comments. Props nbachiyski. see #9112

Timezones format

Another patch, which consolidates time format in timezone options.

(In [10836]) Improve translation support for timezone settings. See #9112 props nbachiyski.