Static map draw exit area (#42)
Fix memory error when backspacing in editor

Negative index being used to access mission objective
descriptions
Fix UI object positions of children of text boxes

Text box positions was not being reset after drawing,
leading to child positions being offset to the end of the
text box.
Add place objective in static map (#42)
Add wrecks in static map (#42)
Refactor line drawing algorithms
Patch AI line clear with Bresenham

AIHasClearLine() is buggy; patch over it by performing
visibility using Bresenham as well. If there is a clear line
of sight between two points, then Bresenham will return
a clear line too.
Replace blue barrel picture

Picture will default to CDogs classic pic if new pic
not available