MXS-1866: Add support for COM_STMT_BULK_EXECUTE

Readwritesplit now detects the COM_STMT_BULK_EXECUTE command and handles
it correctly.

include/maxscale/protocol/mysql.h

@@ -293,6 +293,7 @@ typedef enum
     MXS_COM_STMT_RESET = 26,
     MXS_COM_SET_OPTION = 27,
     MXS_COM_STMT_FETCH = 28,
+    MXS_COM_STMT_BULK_EXECUTE = 0xfa,
     MXS_COM_DAEMON,
     MXS_COM_END
 } mxs_mysql_cmd_t;

server/modules/routing/readwritesplit/rwsplit_internal.hh

@@ -34,6 +34,7 @@ do{ \
 static inline bool is_ps_command(uint8_t cmd)
 {
     return cmd == MXS_COM_STMT_EXECUTE ||
+           cmd == MXS_COM_STMT_BULK_EXECUTE ||
            cmd == MXS_COM_STMT_SEND_LONG_DATA ||
            cmd == MXS_COM_STMT_CLOSE ||
            cmd == MXS_COM_STMT_FETCH ||