Lift out absolute time labels at the beginning of a loop

[ExpHP]

script main {
+1000:
    loop {
0:
        posKeyframe(0.0, 0.0, 0.0);
+10:
    }
}

One might look at this and (not unreasonably) expect that the time at the beginning of the loop body is 0, and therefore, this will wait each iteration after the first time it hits the implicit goto at the end of the loop. However, that goto actually sets the time to 1000, and thus once this enters the loop it will spin infinitely.

We probably want this to be equivalent to:

script main {
+1000:
0:
    loop {
        posKeyframe(0.0, 0.0, 0.0);
+10:
    }
}

(note: +1000: 0: is also a weird thing worth its own discussion, but that's another topic)