bug in proc_wait

lots of cleanup

idecref cwd in exit

delete unused functions
a few comments

test malloc

nit in sbrk
indirect block
fix dup to share fd struct

better parsing of sh commands (copied from jos sh)
cat: read from 1 if no args
sbrk system call, but untested
getpid system call
moved locks in keyboard intr, but why do we get intr w. null characters from keyboard?

cd in shell
nits in mkdir, ls, etc.

each cpu[] has its own gdt and tss
no per-proc gdt or tss, re-write cpu's in scheduler (you win, cliff)
main0() switches to cpu[0].mpstack

so fast interrupts overflow the kernel stack
fix: cli() before lapic_eoi()

give cpu1 a TSS and gdt for when it enters scheduler()
and a pseudo proc[] entry for each cpu
cpu0 waits for each other cpu to start up
read() for files

Eliminate annoying Pseudodesc structure.
Eliminate unnecessary parts of mmu.h.

Rename fd_reference to more suggestive fd_incref.
(Fd_reference sounds like it might just return the ref count.)

Attempt to clean up newproc somewhat.

Also remove all calls to memcpy in favor of
memmove, which has defined semantics when
the ranges overlap.  The fact that memcpy was
working in console.c to scroll the screen is not
guaranteed by all implementations.

New scheduler.

Removed cli and sti stack in favor of tracking
number of locks held on each CPU and explicit
conditionals in spinlock.c.