Add proper `IsEqual()` method to `UserID`

sources/Users/Tests/TEST_User.uc

@@ -55,9 +55,9 @@ protected static function Test_UserID()
     testID3 = UserID(__().memory.Allocate(class'UserID'));
     testID2.Initialize(P("76561198025127722"));
     testID3.Initialize(P("76561198044316328"));
-    TEST_ExpectTrue(testID.IsEqualTo(testID2));
+    TEST_ExpectTrue(testID.IsEqual(testID2));
     TEST_ExpectTrue(testID.IsEqualToSteamID(testID2.GetSteamID()));
-    TEST_ExpectFalse(testID3.IsEqualTo(testID));
+    TEST_ExpectFalse(testID3.IsEqual(testID));
 
     Issue("Steam data returned by `UserID` is incorrect.");
     SteamID = testID3.GetSteamID();

sources/Users/UserID.uc

@@ -244,21 +244,23 @@ public final function SteamID GetSteamID()
     return initializedData;
 }
 
-/**
- *  Checks if two `UserID`s are the same.
- *
- *  @param  otherID `UserID` to compare caller object to.
- *  @return `true` if caller `UserID` is identical to `otherID` and
- *      `false` otherwise. If at least one of the `UserID`s being compared is
- *      uninitialized, the result will be `false`.
- */
-public final function bool IsEqualTo(UserID otherID)
+public function bool IsEqual(Object other)
 {
+    local UserID otherID;
+
     if (!IsInitialized())           return false;
+    otherID = UserID(other);
+    if (otherID == none)            return false;
     if (!otherID.IsInitialized())   return false;
+
     return (initializedData.steamID32 == otherID.initializedData.steamID32);
 }
 
+protected function int CalculateHashCode()
+{
+    return initializedData.steamID32;
+}
+
 /**
  *  Checks if caller `UserID`s is the same as what's described by
  *  given `SteamID`.