* Add `partinfo' type, for description of a single partition,
so we can pass labels by reference..
* Add label.c with label initialization, naive overlap-check code,
and a UI entrypoint edit_and_check_label() which iterates through
checking a label for overlaps, and if any, giving the user the choice of
fixing them or punting back to the main menu.
* Change return type of md_make_bsd_partitions from void to int.
Return 0 if the partition has problems (or the user gave up on it)
and 1 if the partition is completed and looks OK.
* Change install() to check return value of md_make_bsd_partitions().
If it returns zero, print an `abort' message and return to main menu.
* Add label.c to all ports' Makefile.
MD code tested on pmax and cut-and-pasted to other ports.
jonathan