sincos is just a wrapper around the GNU libc sincos. sincosh is the
equivalent for sinh and cosh, but there doesn't seem to be any such
function, so it's just the two wrapped. They both return their results
in a vec2/vec2d as (sih[h], cos[h]).
The old math functions from quake and quakeworld don't belong with the
newer ones as their presence in the same object file causes invalid
builtin warnings when pr_cmds isn't present.
Only as scalars, I still need to think about what to do for vectors and
quaternions due to param size issues. Also, doubles are not yet
guaranteed to be correctly aligned.
