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.

Rearrange proc.h and proc.c to get our action-packed spreads back (mostly).  They also make sense in this order, so it's not just for page layout.

Re-re-arrange bootasm and bootother.  We can't get bootasm and bootmain on the same page, but this will make them easier to flip between.

I totally misunderstood the even/odd spec.  Add some docs, remove my 'left+' hack, and orthogonalize left/right versus even/odd so you can specify them independently.

Slight simplification of copyuvm.  We could simplify other things now that processes are contiguous, but we'd have to think harder about the error paths.

Remove the stack guard page.  Processes are now contiguous from 0 to proc->sz, which means our syscall argument validation is correct.  Add a pointer validation test and remove the stack test, which tested for the guard page.