Small UI fix for "New PostGIS connection" dialog
QPyNullVariant() equals to QPyNullVariant(), qgis.core.NULL

>>>> from qgis.core import NULL
>>>> lyr.getFeatures().next().attributes()[0] == NULL
True
Set min field precision even when hidden (Fix #8480)
[spatialite] Use QVariant::LongLong as int type consistently
Fix some postgres field precision and length inconsistencies