Remove type arg to mknod (assume T_DEV).

Allow multiple arguments to ls.

nits in comments

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

test files with holes (not ok)

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