Fixed a bug where anno -append put the headers in the wrong place

Fixed a bug where anno -append put the headers in the wrong place
if applied to a message that didn't contain any headers.

Added a special value of "all" to the -number option that causes
anno -delete to delete all matching components instead of just
the first one.

Added new -preserve and -nopreserve options.  Using -preserve
retains the original last accessed and last modified times on
annotated messages.