[GRASS5] Region lock

[Radim Blazek]

Does it make sense to add region lock?
Region (WIND file) could be locked by modules until call to
G_get_window and modules changing region (d.zoom, g.region) could check 
if the region is in use.

OTOH,
1) G_get_window is usually called in first rows of main()
    so that user cannot start others module before it is called
2) it does not resolve problem in scripts on background which is
    a real pain

Radim