Normalize robot heading server side
Do not draw damcon arena walls in robot drawing function.
Make add_generic_damcon_object a little more parameterized
initialize damcon object ids
Fix bug in damcon object allocations

Was always using index 0 instead of the allocated index
adjust dimensions of damcon arena
Add damcon systems
Implement Liang-Barsky line clipping algorithm
use clipping algo
calculate bounding boxes for vectorized objects
use bounding boxes for object level clipping

instead of doing object level clipping just based on
the origin of the object.
Make damcon robot move faster
Do not let robot get too close to walls
make robot controllable via mouse
collision-detect-robot-with-systems
Put labels on damcon systems
Rework liang-barsky interface

Current interface has statics in the library, isn't thread safe, etc.
Fix filled rectangle clipping

Replacing the rectangle drawing code with four lines
means that filled rectangles broke.  I was using those
on the Engineering screen, for one.  Well, it's trivial
to clip rectangles, so, do that instead of using lines and
liang barsky.
Improve robot motion model

to enable drifting around corners and control via mouse to work better.
Fix issue with ssgl leaking file descriptors

After awhile, snis_server would complain about accept()
failing due to too many open files.  I think this should
fix that.  I think what was happening was that as the server
tried to update ssgl_server, the write failed because the ssgl
server gave up on it (this may be a separate problem) and then
it leaked the descriptor.