make bounds_checked_int<> check for division by zero
update plane_as_base_point_and_normal comment
Explain a pseudoness thing in polygon_collision_detection.cpp, per Eli
fix a hack in polygon_collision_detection.cpp
units_tests.cpp: eliminate warning
polygon_collision_detection.cpp: use correct integral type
Merge branch 'master' into unitizing1

Conflicts:
	data_structures/polygon_collision_detection.cpp