PJ: remove add_c_stack, assign_c_stack, and push_c_stack.
PJ: remove __STACK_R16__ and __STACK_R32__ definitions.

sob_size formula defined for __STACK_R32__ works in general, e.g.:
16-bit int -> rounds up to next multiple of 2.
32-bit int -> rounds up to next multiple of 4.
PJ: delete memask.c, duplicate of memcask.c.
PJ: delete sintab.c, duplicate of imrotate.c.
PJ: delete sqrroot.c, duplicate of imclcdst.c.