[Quest API] Let HasQuestSub check encounters (#2435)

This fixes an edge case where trading would not detect the npc had a
quest handler if it was registered inside a Lua encounter.

zone/lua_parser.cpp

@@ -1095,6 +1095,19 @@ bool LuaParser::HasFunction(std::string subname, std::string package_name) {
 	return false;
 }
 
+bool LuaParser::HasEncounterSub(const std::string& package_name, QuestEventID evt)
+{
+	auto it = lua_encounter_events_registered.find(package_name);
+	if (it != lua_encounter_events_registered.end()) {
+		for (auto riter = it->second.begin(); riter != it->second.end(); ++riter) {
+			if (riter->event_id == evt) {
+				return true;
+			}
+		}
+	}
+	return false;
+}
+
 void LuaParser::MapFunctions(lua_State *L) {
 
 	try {