Sync translations with transifex
Rename libslab to libmate-slab

https://github.com/mate-desktop/mate-control-center/issues/100

This is to avoid package name and version conflicts with
libslab0 / libslab0a which existed in Debian until squeeze.

MATE components (currently only gnome-main-menu) depending
on libmate-slab0 have to be patch accordingly.