heimdal and BDB troubles after upgrading to 10

[Matt Mullins]

It looks like I've managed to break my KDC by upgrading to 10 -- all I can
seem to get the KDC to do is give me the following error:

2014-02-28T22:46:02 Failed to open database: dbopen (/var/heimdal/foo):
Inappropriate file type or format

I've tried building db5 (replacing db46 which is also still installed on my
machine -- apparently deprecated in the meantime), and rebuilding heimdal
against it, all to no avail.

db_verify-5 reports that the database file is in good health.  gdb tells me
that for some reason, heimdal is trying to use the libc's dbopen() instead
of db5's -- is there a way I can coerce heimdal into using the right
library?

My krb5.conf has:
[kdc]
        database = {
                dbname = /var/heimdal/foo
                realm = LOCAL.MMLX.US
                mkey_file = /var/heimdal/foo.mkey
                log_file = /var/heimdal/bar
                acl_file = /var/heimdal/kadmind.acl
        }
        enable_kereberos4 = false
        enable_http = false