hlink: Fix memory leak by freeing extension services This->headers in the release function.

dlls/hlink/extserv.c

@@ -91,6 +91,7 @@ static ULONG WINAPI ExtServUnk_Release(IUnknown *iface)
     if(!ref) {
         heap_free(This->username);
         heap_free(This->password);
+        heap_free(This->headers);
         heap_free(This);
     }