This will make it possible for the engine to set up their parameter
pointers when running Ruamoko progs. At this stage, it doesn't matter
*too* much, except for varargs functions, because no builtin yet takes
anything larger than a float quaternion, but it will be critical when
double or long vec3 and vec4 values are passed.
This is a nice feature found in fteqcc (also a bit of a challenge from
Spike). Getting bison to accept the new expression required rewriting the
state expression grammar, so this is mostly for the state expression. A
test to ensure the state expression doesn't break is included.
