Define KB_IN_BYTES, MB_IN_BYTES for WP < 4.4.

Author: gitlost

src/DB_Command.php

@@ -633,6 +633,14 @@ public function size( $args, $assoc_args ) {
 
 		if ( ! empty( $size_format ) && isset( $db_bytes ) && ! $tables ) {
 
+			// These added WP 4.4.0.
+			if ( ! defined( 'KB_IN_BYTES' ) ) {
+				define( 'KB_IN_BYTES', 1024 );
+			}
+			if ( ! defined( 'MB_IN_BYTES' ) ) {
+				define( 'MB_IN_BYTES', 1024 * KB_IN_BYTES );
+			}
+
 			// Display the database size as a number.
 			switch( $size_format ) {
 				case 'mb':