Blender Git Loki

Bumping up margin for catching marker events in animation editors.

Old value of 30 px was perhaps a bit too strict, given that scrollbars
took up 16px and that standard icons are 16px, which in total would
have been 32px from the bottom of the region. Having said that, the
marker icons are only about half-size, though it seems that in general
people (can) only aim quite loosely...