Defines starting with `b' in 321/ref_soft

• BACKFACE_EPSILON 321/ref_soft/r_local.h:218
• BBOX_MUST_CLIP_XY 321/ref_soft/r_alias.c:91
• BBOX_MUST_CLIP_Z 321/ref_soft/r_alias.c:92
• BBOX_TRIVIAL_ACCEPT 321/ref_soft/r_alias.c:90
• BBOX_TRIVIAL_REJECT 321/ref_soft/r_alias.c:93
• BMODEL_FULLY_CLIPPED 321/ref_soft/r_local.h:210