tin variety (trunk only)

- store the variety of tin at tin creation time
  rather than at tin-opening time (as a negative
  value in spe just as homemade was; spinach
   is still spe 1)

Allow wishing for a particular variety of tin
from the tin variety list:
	"deep fried", "boiled","broiled","candied"
	"dried", "french fried", "homemade"
	"pickled", "pureed", "rotten", "sauteed"
	"smoked", "soup made from", "stir fried",
	"szechuan"
Example: "tin of soup made from orc"

non-debug player could randomly fail on the
variety specification 1 in 4 times

src/mkobj.c

@@ -425,12 +425,13 @@ boolean artif;
 	    case TIN:
 		otmp->corpsenm = NON_PM;	/* empty (so far) */
 		if (!rn2(6))
-		    otmp->spe = 1;		/* spinach */
+		    set_tin_variety(otmp, SPINACH_TIN);
 		else for (tryct = 200; tryct > 0; --tryct) {
 		    mndx = undead_to_corpse(rndmonnum());
 		    if (mons[mndx].cnutrit &&
 			    !(mvitals[mndx].mvflags & G_NOCORPSE)) {
 			otmp->corpsenm = mndx;
+			set_tin_variety(otmp, 0);
 			break;
 		    }
 		}