Choose containers from a menu when #looting

The ynq prompt is no more; instead, when looting over multiple
containers, players choose which containers to loot from a menu.

The paranoid_loot option now controls if a single container on a space
brings up a menu or skips straight to looting it.

This also causes the bite of a bag of tricks to stop looting of multiple
containers on a single space, as well an exploding bag of holding.
Autoloot after autounlock also stops multi-looting.

query_objlist() can now return -2 if the SIGNAL_ESCAPE flag is sent and
the player cancels the object menu (versus just not choosing anything),
allowing them to skip the adjacent monster loot prompt by pressing the
escape key.
Choose containers from a menu when #tipping

Works the same as the menu for looting, even being controlled by the
paranoid_loot option, except only one container can be chosen.
Choose floor items from a menu when eating, sacrificing and tinning

Eating controls are now like in Slash'EM, replacing the old ynq prompts
for each eligible item on the floor beneath you.

Implementing this actually makes the code cleaner.  Possible future
enhancement: rework the logic in floorfood() to remove the gotos.