This patch extends commit1a47ae24712377821994c3b0309b9437da129d73 and
addresses the following issues:
1) The state of the menu action checkbox was not updated when the other
window changed the its state
2) There should be **no** access to KisConfig in the OpenGL rendering
loop (it is slow due to possible disk access).
3) A canvas update call should be issued right after the config changed,
otherwise the old state of the grid will be visible until one hovers
the canvas
BUG: 389033