Fix compatibility with MySQL 8 - error on 'system' table use

CHANGELOG

@@ -1,6 +1,8 @@
 CHANGELOG Roundcube Webmail
 ===========================
 
+- Fix compatibility with MySQL 8 - error on 'system' table use
+
 RELEASE 1.4-beta
 ----------------
 - Added new skin with mobile support - the Elastic

SQL/mysql.initial.sql

@@ -222,4 +222,4 @@ CREATE TABLE `system` (
 
 /*!40014 SET FOREIGN_KEY_CHECKS=1 */;
 
-INSERT INTO system (name, value) VALUES ('roundcube-version', '2018021600');
+INSERT INTO `system` (`name`, `value`) VALUES ('roundcube-version', '2018021600');

SQL/postgres.initial.sql

@@ -313,4 +313,4 @@ CREATE TABLE "system" (
     value text
 );
 
-INSERT INTO system (name, value) VALUES ('roundcube-version', '2018021600');
+INSERT INTO "system" (name, value) VALUES ('roundcube-version', '2018021600');