tdb2: don't be fascist when TDB_VERSION1 is specified.

tdb2: don't be fascist when TDB_VERSION1 is specified.

We currently insist that a tdb file be a version1 file if tdb_open() is
passed the TDB_VERSION1 flag; we fail if it's actually a tdb2.

But that makes generic wrappers harder, and is unlikely to be what the
user wants: if they do, they can check tdb_get_flags() & TDB_VERSION1
after opening.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
(Imported from CCAN commit 9691464a16ef22d6acadfef209666381dfe22b2f)

Autobuild-User: Rusty Russell <rusty@rustcorp.com.au>
Autobuild-Date: Wed Nov  2 08:38:38 CET 2011 on sn-devel-104