change interface of draw_laserbeam to use coords instead of ships
remove "sxdist2" debug code
fix bug in circle line intersection solver
fix another bug in line circle intersection code
fix yet another line circle intersection bug
do not add laserbeams for torpedoes (was just test code)
begin switching phasers to use laserbeam code
make laserbeams do damage
fix rate limiting of enemy laser fire
make enemies a bit more aggressive