Warning fixes:

- Don't use %lu for size_t; they're different on Linux x86.

- has_warned_about_drivers is only used on win32, so only declare it
  there to avoid a unused variable warning.

Source/Core/DolphinWX/Src/ISOProperties.cpp

@@ -887,7 +887,7 @@ void CISOProperties::OnExtractDataFromHeader(wxCommandEvent& event)
 		}
 		else
 		{
-			PanicAlertT("Partition doesn't exist: %lu", partitionNum);
+			PanicAlertT("Partition doesn't exist: %u", (unsigned) partitionNum);
 			return;
 		}
 	}