This is a step towards making replication a library, such that the 5.6 rpl-lib can be plugged into the 5.5 core [WL#5675]. We will move all replication files to a new subdirectory of sql: - Create a new subdirectory of sql/, sql/rpl/ - Move all replication files from sql/ to sql/rpl/ - Remove the rpl_ prefix from these files.
