Bug#345644: Solution

[Linas Zvirblis <0x0007@gmail.com>]

I should have reported this bug against xlibs. I managed to solve the 
problem by using data from xkb-data (experimental).

After doing...

 export XKBPATH=/etc/X11/xkb-data
 setxkbmap -layout us,lt,ru\(phonetic\) \
  -option 'grp:shift_toggle' -print | xkbcomp -w - :0

...hitting both shifts now correctly changes layout...

 export XKBPATH=/etc/X11/xkb
 setxkbmap -layout us,lt,ru\(phonetic\) \
  -option 'grp:shift_toggle' -print | xkbcomp -w - :0

...breaks it again.

I will repeat myself to make sure it is clear. In both cases I can do...

 setxkbmap -layout whatever

...to switch layouts and it will work. The only thing that does not work 
is grp_anything.