lab2
Remove files that were supposed to be released in lab 3.
Improve serial port input handling.  Based on a suggestion from Evan Broder.
lab3
Kill QEMU harder in the grade script to work around an OS X QEMU bug.

Undo a outdated workaround from the lab 1 grade script, for posterity.
Fix bad output redirection when killing QEMU
Fix 'make qemu' and 'make clean; make qemu' behaving differently after
a grade script run.
lab4
lab5
Remove left-over files from lab 4
lab6
Add user/faultregs test
Add user/faultregs test