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.

src/invent.c

@@ -1488,6 +1488,31 @@ getobj(const char *word,
     boolean oneloop = FALSE;
     Loot *sortedinvent, *srtinv;
 
+    struct _cmd_queue *cmdq = cmdq_pop();
+
+    if (cmdq) {
+        /* it's not a key, abort */
+        if (cmdq->typ != CMDQ_KEY) {
+            free(cmdq);
+            return (struct obj *)0;
+        }
+
+        for (otmp = g.invent; otmp; otmp = otmp->nobj)
+            if (otmp->invlet == cmdq->key) {
+                int v = (*obj_ok)(otmp);
+
+                if (v == GETOBJ_SUGGEST || v == GETOBJ_DOWNPLAY) {
+                    free(cmdq);
+                    return otmp;
+                }
+            }
+
+        /* did not find the object, abort */
+        free(cmdq);
+        cmdq_clear();
+        return (struct obj *)0;
+    }
+
     /* is "hands"/"self" a valid thing to do this action on? */
     switch ((*obj_ok)((struct obj *) 0)) {
     case GETOBJ_SUGGEST: /* treat as likely candidate */