Remove struct uinode.
Remove type arg to mknod (assume T_DEV).

Remove puts in favor of printf.
Allow multiple arguments to ls.

nits in comments

Rework comments a bit.

Move initialization of %sp after
protected mode jump and change to %esp.

test files with holes (not ok)

Use parent pointer instead of ppid.

PDF at http://am.lcs.mit.edu/~rsc/xv6.pdf

Various changes made while offline.

 + bwrite sector argument is redundant; use b->sector.
 + reformatting of files for nicer PDF page breaks
 + distinguish between locked, unlocked inodes in type signatures
 + change FD_FILE to FD_INODE
 + move userinit (nee proc0init) to proc.c
 + move ROOTDEV to param.h
 + always parenthesize sizeof argument