Add assistance to fire-command

Allows the fire-command to autowield a launcher; it will now
do either swapweapon or wield an appropriate launcher, if you
have ammo quivered.

This assistance can be turned off with the fireassist boolean option.

Adds a rudimentary command queue, which allows the code to add keys
or extended commands into the queue, and they're executed as if
the user did them.  Time passes normally when doing the queue,
and the queue will get cleared if hero is interrupted.

include/flag.h

@@ -293,6 +293,7 @@ struct instance_flags {
 #endif
     boolean clicklook;       /* allow right-clicking for look */
     boolean cmdassist;       /* provide detailed assistance for some comnds */
+    boolean fireassist;      /* autowield launcher when using fire-command */
     boolean time_botl;       /* context.botl for 'time' (moves) only */
     boolean wizweight;       /* display weight of everything in wizard mode */
     boolean wizmgender;      /* test gender info from core in window port */