disallow undo when action was sended

we now disallow undoing actions that we already sended over the network.
We also disallow undoing moves when the rng was invoked like it's done
for recruits/recalls already.
revmoved unused code

this typedef was a leftover from my original plan to pass functions to
run_in_synced_context. I decided to pass strings to
run_in_synced_context at some time.
remove outdated comments.