Look for rc files in system config dirs as well

This will allow us to ship package defaults in /usr instead
of /etc.
Move the module cache files below libdir

These files contain architecture-dependent paths, and thus placing
them into sysconfdir causes unnecessary hassle. Now the immodule cache
file is looked for in libdir/gtk-2.0/2.10.0/immodules.cache.

Belated backport of a change that was done in the run-up to 3.0.
Let query utilities update the cache file directly

This is much more convenient for packagers than having to
redirect the output into the cache file, and much less error-prone.
2.24.20
Merge branch 'gtk-2-24' of git://git.gnome.org/gtk+ into gtk-2-24
JOHNE - Bump version number after merge