spearmint: Minor BSPC changes

Variables holding offsetof should be size_t.
Add missing "break" so aasinfo doesn't say "don't know what to do"
Make "float.h" include be <float.h>, cppcheck complained it wasn't found.
spearmint: Make BSPC use q_shared.c/h and q_math.c

There was a lot of duplicate code and hacks for BSPC being separate.

This affects the AAS generation. There are now less planes but nothing else change?
spearmint: Removed some unused code from BSPC