Fixed an ass-load of compile errors, implemented PING(), resolved some dependency issues, fixed the struct mess. Ping is mildly incorrect (only sends signal instead of start, signal, stop), fixing now. also broke some stuff because usart_receive() is being used instead of interrupts. Will be fixed shortly.
Fixed ping. Using txq now, Also fixed some comments. yay.
Merge
Merge pull request #8 from asr1/master

Pull of Alex and Flavia's initial work on reading from bluetooth.
Fixed struct packing in `servo.pulse()`.
Merge branch 'master' of https://github.com/dwtj/mars-rover
Revised `control` to try to get `comm.ping()` demo to work.
Fixed or quelled build errors on rover.
Fixed build problems and started control_mode.

Also removed old David code from `comm.c`. Also moved error code into
r_error.h and r_error.c.
Switched to a more consistent USART naming scheme.
Created path from `control_mode()` to the handlers.
Revised rover to try to get the ping demo to work.
Now tracking `aux.py`.
Restored `aux.py`.
Tracking down bugs in the ping demo.
Tracking down bugs on the `control` side of the ping demo.
Merge branch 'master' of https://github.com/dwtj/mars-rover
Temporarily added manual ping message read/write to main.
Merge branch 'master' of git://github.com/aore/mars-rover into aore-master

Conflicts:
	control/comm.py
	control/servo.py
Merge pull request #6 from dwtj/master

Merge ping fixes