27 Upgrade notes for 4.0.18

Building with libxml2

When building with libxml2, pkg-config is now used instead of xml2-config to detect and use libxml2, as xml2-config is to be removed from libxml2 in the future.

DB character set and collation check

A check for the correct character set and collation is now performed on the database, database tables and table fields during the initial frontend installation. If the check fails a warning message is displayed.

A warning message is also displayed in ReportsSystem information.