[Unix-jun72] 0407 binaries on 1ed

[Tim Newsham]

I added a patch "aout407.patch" for running a.out binaries in the 1ed
kernel.  It could be a little cleaner; if anyone can review it and fix
it up I would appreciate it.  I was able to run "as" and "size",
both of which are 0407 binaries.

This patch isn't applied automatically, but I also changed the 
"tools/rebuild" script to take a list of optional patches to apply, so now 
you can select any set of optional patches on the command line:

    $ tools/assemv7 cold
    $ tools/assemv7 aout407
    $ tools/assemv7 cold aout407 myowncustompatch

Tim Newsham
http://www.thenewsh.com/~newsham/