Problems with ctm this morning

[Stephen Montgomery-Smith]

I changed the delta generating computer from FreeBSD 7 to FreeBSD 8.
This has caused a couple of problems:

1.  I forgot to update ctm_dequeue, so it failed with some library not
found errors.  So a couple of deltas were not emailed this morning.

2.  mkctm is failing once in a while.  I think it is because mmap does
not allow the length of space allocated to be zero.  (Presumably in
FreeBSD 7 this was allowed.)  I'll try to fix it soon.