[QGIS-Developer] Minimum SpatiaLite version 4.2

[Matthias Kuhn]

Hi devs,

I just proposed an upgrade to SpatiaLite>=4.2 requirement on QGIS 3
(https://github.com/qgis/QGIS/pull/5636)

Is there anyone requiring support for older versions? If yes, we can
also keep compatibility with 4.0/4.1 and just drop code for <4.0 (I
guess that's really outdated nowadays)

Thanks for feedback and best regards

Matthias