freetdm: added threaded media to the TODO

libs/freetdm/TODO

@@ -11,3 +11,12 @@
   cannot be shown to end users, we already provide extensive logging for problem
   troubleshooting.
 
+- Implement threaded IO.
+  Currently IO modules only work on-demand, where the user (ie, FreeSWITCH) drives the read/write
+  of media. If the user stops reading, some functions are not possible 
+  (DTMF detection or Hangup tone detection). It would be useful to implement a FreeTDM mode
+  where the media is driven by a group of threads that are always reading (and possibly writing)
+  then when the user does ftdm_channel_read(), the media would be read from the buffers filled
+  by the media thread and not from the underlying IO device, this gives a chance to FreeTDM to
+  still perform hangup detection or other media services even if the application is not reading.
+