Preliminary attempt at argument passing.  Attempts to convert what used to just be a filename into an entire command string that is parsed and then the stack is setup with the arguments.  Not compiled.  Not tested. Not looking forward to doing so.
Fixed bug where stack wasn't setup yet so calling pushl is not a valid thing to do.
Removed optimizations to make debugging easier
Merge branch 'argument_passing' into system_calls.  Also had to pull up splitting command string into filename and extra arguments before creating thread so the thread can have the correct filename.  Tested with echo and it works.

Conflicts:
	src/userprog/process.c