Further optimizations about physics.inc

[uPeppe]

Thanks for the tip! I didn't know about the VectorSize function introduced in last SA-MP builds

I think that "IsObjectInSphere" function is slow because it is written very badly (there's no need of using floatsqroot, floatabs and floatpower functions). Ideally it should be written like this:
`IsObjectInSphere(objectid, Float:x, Float:y, Float:z, Float:radius2)
{
new Float:x1, Float:y1, Float:z1;

if (GetObjectPos(objectid, x1, y1, z1))
{
    x1 -= x;
	y1 -= y;
	z1 -= z;
    return (x1 * x1 + y1 * y1 + z1 * z1) < (radius2 * radius2);
}
return 0;

}`