For compilers that seem to do the wrong thing(tm).

Speculative fix for:

  segfault at 1 ip b72145d3 sp b58f8bfc error 4 in libc-2.11.3.so

  #0  0xb7a5d5d3 in vfprintf () from /lib/i686/cmov/libc.so.6
  #1  0xb7a7cec7 in vasprintf () from /lib/i686/cmov/libc.so.6
  #2  0xb7dd7c5b in switch_vasprintf (...)
  #3  0xb6296de2 in ftdm_logger (...)
  #4  0xb621625d in misdn_handle_mph_information_ind (...) at ftmod_misdn.c:658
Signed-off-by: Stefan Knoblich <stkn@openisdn.net>