Functionality of system calls:
- Test argument passing on PintOS command line.
3	args-none
3	args-single
3	args-multiple
3	args-many
3	args-dbl-space

- Test "create" system call.
3	create-empty
3	create-long
3	create-normal
3	create-exists

- Test "open" system call.
3	open-missing
3	open-normal
3	open-twice

- Test "read" system call.
3	read-normal
3	read-zero

- Test "write" system call.
3	write-normal
3	write-zero

- Test "close" system call.
3	close-normal

- Test "exec" system call.
5	exec-once
5	exec-multiple
5	exec-arg
5	exec-large-arg

- Test "wait" system call.
5	wait-simple
5	wait-killed
5	wait-twice
5	wait-bad-child

- Test "exit" system call.
5	exit

- Test "halt" system call.
3	halt

- Test recursive execution of user programs.
15	multi-recurse

- Test read-only executable feature.
3	rox-simple
3	rox-child
3	rox-multichild
