Remove unwanted functions from python bindings.

[Richard Boulton]

The python bindings currently expose three functions corresponding to some static methods, which should be instead be addressed through classes (and can indeed currently be addressed through classes, too)::

• Document_unserialise(...)
• Query_unserialise(...)
• Stem_get_available_languages(...)

The first two of these are new in trunk, and should certainly be removed before 1.1.0 (probably just by calling del at the end of xapian.py, if no cleaner solution can be found).

The third should also be removed, but possibly should go through the normal deprecation period first, since (I assume) it's been around for a while.

[Richard Boulton]

Removed the first two (in r12016) and deprecated the third (in r12017).

[Olly Betts]

Stem_get_available_languages() doesn't seem to be an advertised API, and there's a replacement which works with both old and new versions, and I didn't find any uses in Google's codesearch. But it's not a big deal to carry it round as deprecated for a release cycle (removing it ironically adds a line of code!), so I guess we probably should.