Berkeley DB 6 license

[andyj]

While working on some extension build scripts I discovered that the Berkeley DB 6.0.20+ license isn't really free compatible. Can we back up to 6.0.19?. Otherwise I think we should consider dropping it all together. In the mean time I'm going to unsupport it in the extensions I maintain.

[Juanito]

I don't think it would be a problem to go back to 6.0.19