ibar: try to get a better min size
ibar: try to get a better min size

There are two cases, on a shelf and on the desktop.
If on a shelf we are using the height setting of the self, since max.w
max.h are only set after a few calcuations, and the gadget does not get
moved on a shelf which does not fade out, so the first min size
calculation must be correct.
If we are on the desktop max.w and max.h are not always 0.
There were some cases when none of this conditions are met. So this
patch enforces a mimum size of 40x40 pixels.

rvandegrift/e,rvandegrift/e,rvandegrift/e