Merge "Add new recentchanges field rc_source to replace rc_type"

diff --cc RELEASE-NOTES-1.22
Simple merge

diff --cc includes/installer/MysqlUpdater.php
Simple merge

diff --cc includes/installer/PostgresUpdater.php
Simple merge

diff --cc includes/installer/SqliteUpdater.php
Simple merge

diff --cc maintenance/postgres/tables.sql
Simple merge

diff --cc maintenance/tables.sql
Simple merge