Passes usertests and stressfs
Seems to recover correctly in a number of simple cases

At some point between gcc 4.4 and 4.6, omitting the frame pointer
became default if any -O is specified.  getcallerpcs relies on the
frame pointer, so bring it back.

[ cherry-picked de6075ff0978108daea1d658425bcb37663a98a0 ]

Conflicts:

	fs.c

does not affect line numbers

Variable declarations at top of function,
separate from initialization.

Use == 0 instead of ! for checking pointers.

Consistent spacing around {, *, casts.

Declare 0-parameter functions as (void) not ().

Integer valued functions return -1 on failure, 0 on success.

fix double iunlockput

usertest that passes too many arguments, break exec

delete most comments from bootother.S (since copy of bootasm.S)
ksegment() -> seginit()
move more stuff from main() to mainc()

Simplify allocuvm/deallocuvm to operate in a contiguous memory model.  This makes their interface match up better with proc->sz and also simplifies the callers (it even gets the main body of exec on one page).

Rearrange vm.c so it's in logical order and prints nicely.  Shorten a few functions in uninteresting ways to make them fit.