Functionality of system calls:

- Test argument passing on Pintos command line.

5	args-none
5	args-single
5	args-multiple
3	args-many
3	args-dbl-space

- Test "create" system call.

5	create-empty
5	create-long
5	create-normal
5	create-exists

- Test "open" system call.

5	open-missing
5	open-normal
5	open-twice

- Test "read" system call.

5	read-normal
5	read-zero

- Test "write" system call.

5	write-normal
5	write-zero

- Test "close" system call.

5	close-normal

- Test "exec" system call.

5	exec-once
5	exec-multiple
5	exec-arg

- Test "wait" system call.

5	wait-simple
5	wait-twice

- Test "exit" system call.

5	exit

- Test "halt" system call.

5	halt

- Test recursive execution of user programs.

15	multi-recurse

- Test read-only executable feature.

5	rox-simple
3	rox-child
3	rox-multichild