gitk: Add keybinding to switch to parent commit

Signed-off-by: Max Kirillov <max@max630.net>
Signed-off-by: Paul Mackerras <paulus@samba.org>
gitk: Updated Bulgarian translation (302t,0f,0u)

Signed-off-by: Alexander Shopov <ash@kambanaria.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>
Merge branch 'master' of git://ozlabs.org/~paulus/gitk

* 'master' of git://ozlabs.org/~paulus/gitk:
  gitk: Updated Bulgarian translation (302t,0f,0u)
  gitk: Add keybinding to switch to parent commit