Fix clipsize being retained from stock items

It looks like something in CTFPlayer::ManageRegularWeapons depends
on the item definition being accurate for the clip size.

There's probably a better way to handle this in ::ItemsMatch() now
that it's clear what it actually does, so we should review that
in the future.

Fixes #56.

scripting/cwx.sp

@@ -482,6 +482,16 @@ MRESReturn OnManageRegularWeaponsPre(int client, Handle hParams) {
 			continue;
 		}
 
+		int currentitemdef = GetEntProp(storedItem, Prop_Send, "m_iItemDefinitionIndex");
+		if (TF2Econ_GetItemLoadoutSlot(currentitemdef, playerClass) != -1) {
+			// only replace the itemdef if the existing one is not valid for the class
+			// this is because something something static attribute retention
+
+			// we should probably just drop support for invalid weapons at this point;
+			// it's starting to be a headache to manage
+			continue;
+		}
+
 		// replace the itemdef and classname with ones actually valid for that class to skirt
 		// around the ValidateWeapons checks
 		char classname[64];