Keyboard layout settings: /usr/share/X11/xkb/rules/base.extras.xml

[Vovanium]

Expected Behavior

There's a file /usr/share/X11/xkb/rules/base.extras.xml (on Linux, other systems may have a different path) which contains some extra keyboard layouts in addition to those in base.xml. I want to have those extra layouts available in the Keyboard Layout Settings.

Current Behavior

Only base.xml is read, and only layouts from it are available.

Possible Solution

Read base.extras.xml in addition to base.xml on systems have that one.

Context

I'm using one of those keyboard layouts listed in base.extra.xml, and configuring it through Settings is not possible. It can be set through Settings Editor, but it is tricky.
I don't know if the mentioned file is available on all systems (I'm using Gentoo Linux), so it may require some work to keep the code cross-platform.

[tsujan]

Duplicate of #748