Since spir-v needs actual bools for its conditional instructions, the
time to do bool properly finally came. As expected, the changes caused
quite a mess, but Ruamoko now does bool/true/false.
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.
