* emcd.c:
   - minor changes, mostly comments. this is next to fix up.
* vmc-client.c:
   - minor changes to tell vmcd about the last packet in a frame
processing cycle (via MTP_POSITION_STATUS_CYCLE_COMPLETE being set in the
last update_position packet of a frame processing cycle).
   - maybe other stuff...
* vmcd.c:
   - massive changes to handle tracking of robots from data passed from
vmc-client, and to handle ID association.
* mtp.h:
   - addded MTP_POSITION_STATUS_CYCLE_COMPLETE #define
   - updated structs request_id and update_id to include a `request_id'
field so that we can uniquely track requests (since they're asynchronous).
* mtp.c:
   - revamped code for above mtp.h changes.