Translations:Keyboard layout switching/79/en

There are two things to note with this entry:
 * It is of type "CTRL+ALT"; it thus takes the standard four shift key settings with and, plus a fifth setting of +. Since the goal is to use ++, and there is no suitable existing type, a new one needs to be created.
 * The "action"  is just a defined symbol in the xkb system. Its semantics are given to it by an entry in a file in the  directory, namely . There is no symbol   (or higher) - instead, steal the otherwise unused existing symbols F13, F14, ..., F24.