* Moved several machine lifecycle callbacks to the notifier/subscriber
model. The old callback registration model is still available for
them for now, but prints a deprecation warning.
* Added pre-save/post-load notifications.
* Use a single allocated timer rather than one anonymous timer per
waiter. Waiters no longer prevent saved states from being loaded.
* Clean up outstanding waiters on stop or state load rather than just
leaking them.
* Started documenting parts of the emulator interface object that should
be relatively stable.
-imagedev/avivideo.cpp: Fixed an object leak on unload. Also changed
some other media image devices to use smart pointers.
Made the sound manager mute controls readable, and got rid of system
enable since it just controls system mute anyway. This was causing
confusion: phantom2 was trying to use both independentlyt casuing the
mute bit to be ignored.
THe Lua interface changes are mostly changing methods to properties,
some renames to make things clearer, and some additional properties for
better control over snapshots.
