[m-dev.] diff: extras/trailed_update enhancements + bug fixes

[Tyson Richard DOWD]

Fergus Henderson wrote:
> 
> Various bug fixes and enhancements to var.m and other stuff in
> extras/trailed_update.

Fergus, either my mail got chopped and your signature was lopped onto
the end, or you forgot to include the diff (again ;-).

-- 
       Tyson Dowd           #          Another great idea from the 
                            #            people who brought you
      trd at .cs.mu.oz.au      #               Beer Milkshakes!
http://www.cs.mu.oz.au/~trd #	         Confidence --- Red Dwarf