Updates for alignment rounding. XXX this is highly machine dependent and

Updates for alignment rounding.  XXX this is highly machine dependent and
should probably be moved to i386/i386/link_machdep.c (and the same for the
alpha).
Implement "deleting" a preloaded module by destroying it's tags. This is a
hack.  We cannot reuse the data, it's been destroyed by relocation,
statically initialized variables have been modified, etc.  Note that to
reclaim the load space is going to be more machine-dependent work.
Implement a relocate hook for machdep.c to call so that the physical
addresses get converted to the equivalent KVM addresses.