Extend the range of the 'group_names' patterns which is currently
restricted to typical ones like
pc+us+ru:2+de:3+ba:4+inet
to more general ones such as
macintosh_vndr/apple(alukbd)+macintosh_vndr/jp(usmac)+macintosh_vndr/jp(mac):2
so that the keyboardlayout widget can handles all possible patterns
returned by awesome.xkb_get_layout_group().
I'm working on something that adds :layout functions to widgets. This clashes
with the keyboardlayout widget's use of an entry with this name. This change
adds an underscore as a prefix to the private data members of the
keyboardlayout.
Signed-off-by: Uli Schlachter <psychon@znc.in>