Wt 4.3.0 RC 1

This is the first and likely last release candidate Wt 4.3.0. Among other things, Wt 4.3.0 adds the ability to redirect logging to a custom logging function, and adds login and transport encryption support to the mail client. Check the release notes for more info.

Changes in the Windows builds:

• Updated OpenSSL from version 1.1.1d to version 1.1.1e
• Updated Boost version to 1.72.0 (from 1.71.0)