github issue #1201 - Forcefighting webs

Issue reported by Umbire:  suggestion to always destroy adjacent webs
via 'F'<dir> if wielding Sting or Fire Brand.

Sting already did that; this adds Fire Brand.

This also augments the #untrap command when wielding either of those,
or any other blade.  And rephrases successful untrap message
"You remove {the or your} {bear trap or webbing} from Fido." to
"You extract Fido from {the or your} {bear trap or web}." since the
trap remains intact.

Forcefight and #untrap against webs ought to be reconciled to remove
[some of] their differences and/or share code.  But not by me...

Closes #1201

src/hack.c

@@ -1915,10 +1915,11 @@ domove_fight_web(coordxy x, coordxy y)
                chance to succeed rather than maybe make two tries */
             roll = rn2(uwep ? 20 : (45 - 5 * wskill_minus_2));
 
-        if (uwep && u_wield_art(ART_STING)) {
+        if (uwep && (u_wield_art(ART_STING)
+                     || (uwep->oartifact && attacks(AD_FIRE, uwep)))) {
             /* guaranteed success */
-            pline("%s cuts through the web!",
-                  bare_artifactname(uwep));
+            pline("%s %s through the web!", bare_artifactname(uwep),
+                  u_wield_art(ART_STING) ? "cuts" : "burns");
 
         /* is_blade() includes daggers (which are classified as PIERCE)
            but doesn't include axes and slashing polearms */