BSPC: Fix compile flags

Linux release build was broken, mingw didn't set debug or release flags.

-ffast-math changes AAS files, other(s) made converting bsp to aas go slower so just remove them.
Fix "Bad surface tesselated" in release builds (issue #65)

Introduced in ioq3ztm r291, it's a bug in ET source code.

gen isn't pointing to a srfGeneric_t if not SF_TRIANGLES, SF_GRID, or SF_FOLIAGE.
Writting to it causes unknown memory to be overwritten.