FreeTDM: Add gcc printf()-style format string checks to ftdm_log(), also add FTDM_(U)INT64_FMT and FTDM_TIME_FMT constants.

The format string checks already caught a couple crash-worthy bugs and this
commit fixes a couple more.

Also includes __ftdm_check_scanf(), for completeness (currently unused).

Signed-off-by: Stefan Knoblich <stkn@openisdn.net>

libs/freetdm/src/include/ftdm_os.h

@@ -53,6 +53,8 @@ extern "C" {
 
 /*! \brief time data type */
 typedef uint64_t ftdm_time_t; 
+/*! format string for ftdm_time_t */
+#define FTDM_TIME_FMT FTDM_UINT64_FMT
 
 /*! \brief sleep x amount of milliseconds */
 #ifdef __WINDOWS__