* Added crash fixes for loading old files with Actions/Armatures in them. Was caused by usage of some old globals still and the functions in question not performing NULL checks on the validity of the data they're given.
* Added back reorganise action channels tools (shift/ctrl-shif pageup/down) for Action Editor. These are only available in 'Action Mode' only.
* Tidied up Action Editor/Dopesheet tools code - removed various unused things, and also, added an API call in anim_deps.c to send the correct notifiers, since I anticipate that they're likely to require a few context checks which would be better to centralise than copy+paste everywhere.
Note to Ton: could you have a look at this notifier stuff here? I'm not sure which ones I should be sending...
* Also added a few assorted comments in various places
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