Log Message:
bdb.buildlink3.mk is used to select a Berkeley DB implementation for
use by pkgsrc.  It will automatically depend on either db, db3, or db4
if the native one isn't sufficient.  The two variables that control its
behaviour are:

BDB_DEFAULT is a user-settable variable whose value is the default
       Berkeley DB implementation to use.

BDB_ACCEPTED is a package-settable list of Berkeley DB implementations
       that may be used by the package.

E.g., if you always want to use DB4 as the Berkeley DB for all of the
packages, then you can just set:

	BDB_DEFAULT=	db4

in your /etc/mk.conf.

Packages that currently include db*/buildlink3.mk should be made to
include bdb.buildlink3.mk instead.