This patch fixes the freeze in stage2. There is possible race though as I'm not
sure about the behaviour in the following case:
loader forks and execs stage2
loader sets the pgrp for stage2
stage2 get to the first stdio read
... freeze? kernel stops stage2 process
loader sets the pgrp for it's tty
... does kernel unfreezes stage2 and lets it continue?
This might also break our advanced debugging stuff, but we need the text mode
to work first so that case might get handled when we get that problem.