cyrus-sasl-2.1.22 BerkeleyDB version check

[Alexey Melnikov]

Howard Chu wrote:

> We're getting a lot of crashes reported by users who linked OpenLDAP 
> and libsasl2 with different versions of BerkeleyDB. It would probably 
> help if the sasldb code had the same kind of version check that we use 
> in our code, so that the problem can be caught immediately instead of 
> mysteriously arising somewhere during runtime.

Howard,
I think this check would be better done in _sasl_check_db() which is 
called only once when the plugin is loaded.
Do you agree?