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?

renumber system calls (run gmake clean!)
skeleton for dup system call

cd in shell
nits in mkdir, ls, etc.

stat

no more cons_put system calls
usertests tests two processes writing files

primitive ls

sh accepts 0-argument commands (like userfs)
reads from console

convert userfs to use printf
bfree
ifree
writei
start on unlink

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

Add user.h for prototypes.
Add cons_puts for cleaner output.