First draft of some kind of Action Queue (just like the globalstep queue in to_update), but more flexible and also including delay functionality (mesecon_delayer).
The queue is also saved to a file, so that when restarting mesecons, delayers resume to the state they had when the game shut down. Needs testing.
Try to fix gateswith serverstep code.
Fix the bugs spotted by Novatux - thanks for spotting them
Add ActionQueue priority system
This makes effectors nearer to the source of the action (the receptor) update first.

This defines behaviour for this piston circuit: http://i.imgur.com/9Pp2Mzb.png
And defines, that this memory circuit does not work from this direction: http://i.imgur.com/jJn0aFh.png
But it will work when using the switch from the other side: http://i.imgur.com/nvw0oZB.png

Only if two effectors have the same distance, there is nothing we can do about it, behaviour is not defined.
"Distance" is determined by the stack size of recursions in turnon / turnoff.
Priorities are between 0 (lowest) and 1 (highest).
Fix ActionQueue delays
Fix unloaded area in receptor_off, yet it was only fixed in receptor_on
Resume turnon/off calls as soon as area is loaded in case turnon/off calls end in unloaded territory
Fix infinite priority bug in mesecon:turnoff, thanks to Novatux
Turnon/turnoff overwritable
Actionqueue tweaks
Make receptor_on/off overwritable, fix a serious bug.
Merge pull request #142 from Novatux/actionqueue

Action Queue bugfixes by Novatux
Merge pull request #144 from Novatux/gates-fix

Fix gates with serverstep code.
Let's give that a try.
Fix delayers and disable resuming if not using MESECONS_GLOBALSTEP
Merge branch 'actionqueue'
This introduces the ActionQueue, a new kind of MESECONS_GLOBALSTEP.
Circuits using delayers will now resume when restarting the server.
Also, large circuits should automatically resume if parts of them are
in unloaded chunks.
Old circuits e.g. using gates will not resume when mesecons is updated,
which means you have to restart them once. But after that, it should work
just like it used to.
This will fix a lot of stuff but may also introduce some new bugs.
So please report them!