MXS-1398: Clean up mysql.h header

Cleaned up the MaxScale version of the mysql.h header by removing all
unused includes. This revealed a large amount of dependencies on these
removed includes in other files which needed to be fixed.

Also sorted all includes in changed files by type and alphabetical
order. Removed explicit revision history from modified files.

server/modules/protocol/MySQL/MySQLBackend/mysql_backend.c

@@ -13,15 +13,16 @@
 
 #define MXS_MODULE_NAME "MySQLBackend"
 
-#include <maxscale/protocol/mysql.h>
+#include <maxscale/alloc.h>
 #include <maxscale/limits.h>
 #include <maxscale/log_manager.h>
-#include <maxscale/modutil.h>
-#include <maxscale/utils.h>
-#include <mysqld_error.h>
-#include <maxscale/alloc.h>
 #include <maxscale/modinfo.h>
+#include <maxscale/modutil.h>
+#include <maxscale/poll.h>
 #include <maxscale/protocol.h>
+#include <maxscale/protocol/mysql.h>
+#include <maxscale/router.h>
+#include <maxscale/utils.h>
 
 /*
  * MySQL Protocol module for handling the protocol between the gateway