[hypermail] checkins for trio; folder_by_date with -u

 I've checked in changes to switch from mprintf calls to Trio. I haven't yet removed mprintf.c, but I will probably do so before long.  I've also made changes to allow incremental update with folder_by_date on an empty archive, and to improve error messages for missing gdbm file with folder_by_date on incremental updates of non-empty archives.

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Peter McCluskey          | Fed up with democracy's problems? Examine Futarchy:
http://www.rahul.net/pcm | http://hanson.gmu.edu/futarchy.pdf or .ps