fix missing return, tweaked attachtest to show suspend/resume speed in a sensible manner

library/DFHackAPI.cpp

@@ -983,6 +983,7 @@ int32_t API::ReadCreatureInBox(int32_t index, t_creature & furball,
         }
         index++;
     }
+    return -1;
 }
 
 bool API::ReadCreature(const int32_t &index, t_creature & furball)

tools/attachtest.cpp

@@ -65,10 +65,11 @@ int main (void)
     cout << "Testing suspend/resume"  << endl;
     DF.Attach();
     time(&start);
-    for (int i = 0; i < 100; i++)
+    for (int i = 0; i < 1000000; i++)
     {
         DF.Suspend();
-        cout << "Try " << i << endl;
+		if(i%10000 == 0)
+			cout << i / 10000 << "%" << endl;
         DF.Resume();
     }
     time(&end);