Fix: consume_tin() bypassed is_edible()

Draugr race cannot eat anything except non-veggie corpses and eggs,
meaning no processed foods, which includes anything in a tin. Players
could bypass that rule by using a tin opener to open a tin. This commit
closes that loophole, and forces consume_tin() to check whether the
contents are edible or not.

This isn't the most elegant solution - currently this treats all tins in
any state as off-limits to Draugr. Which is fine for now, because
any food found within a tin is technically processed/preserved. In the
future, I think it'd be neat to allow Draugr to eat meat from a tin if
its contents were rotten (side note: food sense [from spell/as a Hobbit]
should be able to tell if the food inside a tin is rotten or not before
eating it).

Author: k21971

doc/evilhack-changelog.md

@@ -3527,4 +3527,5 @@ The following changes to date are:
   (player is a knight) would stay tame
 - Fix: noncorporeal monsters were affected by knockback
 - Fix: monster could go berserk if temporarily sleeping or paralyzed
+- Fix: consume_tin() bypassed is_edible()
 

src/eat.c

@@ -1543,7 +1543,15 @@ const char *mesg;
             what = the(what);
 
         pline("It smells like %s.", what);
-        if (yn("Eat it?") == 'n') {
+        if (!is_edible(tin)) {
+            You("cannot eat that!");
+            if (flags.verbose)
+                You("discard the open tin.");
+            if (!Hallucination)
+                tin->dknown = tin->known = 1;
+            tin = costly_tin(COST_OPEN);
+            goto use_up_tin;
+        } else if (yn("Eat it?") == 'n') {
             if (flags.verbose)
                 You("discard the open tin.");
             if (!Hallucination)
@@ -1590,7 +1598,13 @@ const char *mesg;
             tin->dknown = tin->known = 1;
         }
 
-        if (yn("Eat it?") == 'n') {
+        if (!is_edible(tin)) {
+            You("cannot eat that!");
+            if (flags.verbose)
+                You("discard the open tin.");
+            tin = costly_tin(COST_OPEN);
+            goto use_up_tin;
+        } else if (yn("Eat it?") == 'n') {
             if (flags.verbose)
                 You("discard the open tin.");
             tin = costly_tin(COST_OPEN);