Use uint64_t and FTDM_UINT64_FMT for flagval and "%u" for unsigned int.
Extend invalid channel id check to cover chan_id == 0 case.

Use ftdm_strlen_zero() and ftdm_array_len() instead of open-coding them.
Move some variables from global scope into local subcommand scope.

Various other little format string and variable naming fixes.
Signed-off-by: Stefan Knoblich <stkn@openisdn.net>