Fix a subtle configure problem where, if gdbm libraries are present on the
system at build time, they are silently chosen in preference to the
standard system db ver1 code. This tends to break a multitude of things
that expect the user* databases to be in db1 format.
Discovered whilst hunting down a really wierd operational bug with exim
using the imappw entry for SMTP AUTH.
Add an explicit WITH_GDBM knob to turn on the use of gdbm files, since the
code is present in the source, but default to off, forcing the use of
Submitted by: ade
Approved by: maintainer timeout