'f'ire revamp

The fire command could claim that time passed when it hadn't (fill
quiver with ammo, which takes no time, then queue commands to switch
to matching launcher, which should also take no time while queueing,
only during subsequent execution).

If quiver is empty or has ammo in it, give wielded thrown-and-return
weapon (aklys) priority over filling quiver or switching to ammo's
launcher.  Don't do that if quiver has non-ammo in it, otherwise
players running Valks who wield Mjollnir with super strength but
want to throw quivered daggers would complain.

When player is being asked what to fill the quiver with, use the
\#quiver command to do that.  Using it honors a count to split a
stack, handles switching uwep or uswapwep to uquiver, and gives
feedback.  This is actually a fairly substantial change.

For 'fireassist', when switching to a launcher that isn't already
uswapwep pick one known to be blessed or uncursed over one having
unknown BUC status.  But use the latter as last resort.

include/extern.h

@@ -3134,6 +3134,7 @@ extern void setuswapwep(struct obj *);
 extern int dowield(void);
 extern int doswapweapon(void);
 extern int dowieldquiver(void);
+extern int doquiver_core(const char *);
 extern boolean wield_tool(struct obj *, const char *);
 extern int can_twoweapon(void);
 extern void drop_uswapwep(void);