No replys yet, but here's a thought (dont have time to test it right now)
Example:
Rotate an angle to point from elbow to target, rotate the first bone by that angle,
then for the bicep bone...

Get a dummy angle to point from shoulder to target, and get another to point from shoulder to wrist (those are two angles from two vectors) and then use ang_diff to get the difference and rotate the bicep bone with the difference.

Those two operations repeated over and over will turn an arm towards a point in space...
For more bones, the procedure for the bicep bone is repeated for every bone, turning an angle towards the target, an angle towards the last bone in the chain (effector, or eg. a finger) and turn that bone by the difference of those two angles and go to next bone or iteration.

Gonna test it tonight, if I have the time...