evas box - fix longstanding bug where min size is miscalculated

evas box - fix longstanding bug where min size is miscalculated

this has affected edje for... like... ever. min size of boxes just
doesnt work. because evas box just doesnt do it right. this has led to
nasty things where edje box is just not usable if you use weight of 0.
btw weight 0 means "stay at min size no matter what even if we expand
the box to be bigger" in edje... which is totally broken and i can't
fix that without potentially breaking even more stuff... but let's
see. i've been using this for several days now and ... i can't find
breakage... so this should fix up SOME issues in edje.

@fix