girepository: Use expected signed types for iterating

We are using various indexes types, but not always using the correct
sign or size, so let's adapt this to ensure we're consistent with the
values we're comparing with.

girepository/giinterfaceinfo.c

@@ -323,10 +323,10 @@ GISignalInfo *
 gi_interface_info_find_signal (GIInterfaceInfo *info,
                                const char      *name)
 {
-  unsigned int n_signals;
+  uint32_t n_signals;
 
   n_signals = gi_interface_info_get_n_signals (info);
-  for (unsigned int i = 0; i < n_signals; i++)
+  for (uint32_t i = 0; i < n_signals; i++)
     {
       GISignalInfo *siginfo = gi_interface_info_get_signal (info, i);