Crashfix: move spatial, AI queries in map-widget

Crashfix: move spatial, AI queries in map-widget

In threaded OSG drawing, MapWidget::draw runs in the render
thread context, but touches lots of main thread state. Move most of the
work to an update() helper run on the main thread instead, so draw()
mostly makes pure GL calls.

(This is a fix for 3.0, the real solution is to migrate to a
Canvas-based map and GUI)