Update ec_mingw.c

* Removed strtok_r() as this now is in ec_strings.c.
* Removed inet_pton() as this now is in missing/inet_pton.c.
* Removed 'USE_GETTEXT' condition in 'get_winsock_error()'.
* 'setup_console()' does nothing when 'IM_A_GUI_APP' is not defined (as in a plugin or an 
  utils program). '-DIM_A_GUI_APP' should set only when GTK-support is built.
* I have some doubts that 'LoadLibrary ("exchndl.dll")' makes any sense in a modern gcc 
  (debug-format is a moving target among the gnu folks. '-gdwarf-2' unsupported in DrMingW?).