Detect foreign tables in 2.3.x upgrade, print error and skip

1/ install Moodle 2.2 with 'mdl_' prefix 2/ add bogus tables with names: 'mdl_111user', 'mdl_user-bak', 'mdl_userBak' 3/ create with 'mdl_tableview' from any other table such as "create view mdl_tableview as select * from mdl_config" 4/ expected warnings during upgrade to 2.3 or master branch: Database table with invalid name 'mdl_111user' detected, skipping. Database table with invalid name 'mdl_user-bak' detected, skipping. Database table with invalid name 'mdl_userBak' detected, skipping. Unsupported database table view 'mdl_tableview' detected, skipping.