mouse line would reset to 0/0/0
a few areas that use ED_view3d_win_to_segment_clip() didnt take into account the case where the segment was filly clipped, some callers even needed the segment not to be clipped.
- added ED_view3d_win_to_segment()
- ED_view3d_win_to_segment_clip() now returns FALSE if the segment is totally clipped, but the start/ends of the line are not zero'd as they were before.
- move object_iterators.c --> view3d_iterators. (ED_object.h had to include ED_view3d.h which isn't so nice)
- move projection functions from view3d_view.c --> view3d_project.c (view3d_view was becoming a mishmash of utility functions and operators).
- some some cmake includes as system-includes.