Add MySQL stricton changes to mysqli and pdo/mysql drivers
diff --git a/system/database/drivers/mysqli/mysqli_driver.php b/system/database/drivers/mysqli/mysqli_driver.php
index 3436682..f8694b9 100644
--- a/system/database/drivers/mysqli/mysqli_driver.php
+++ b/system/database/drivers/mysqli/mysqli_driver.php
@@ -84,7 +84,7 @@
 	 *
 	 * @var	bool
 	 */
-	public $stricton = FALSE;
+	public $stricton;
 
 	// --------------------------------------------------------------------
 
@@ -137,9 +137,26 @@
 
 		$this->_mysqli->options(MYSQLI_OPT_CONNECT_TIMEOUT, 10);
 
-		if ($this->stricton)
+		if (isset($this->stricton))
 		{
-			$this->_mysqli->options(MYSQLI_INIT_COMMAND, 'SET SESSION sql_mode="STRICT_ALL_TABLES"');
+			if ($this->stricton)
+			{
+				$this->_mysqli->options(MYSQLI_INIT_COMMAND, 'SET SESSION sql_mode = CONCAT(@@sql_mode, ",", "STRICT_ALL_TABLES")');
+			}
+			elseif (version_compare($this->version, '5.7', '>='))
+			{
+				$this->_mysqli->options(MYSQLI_INIT_COMMAND,
+					'SET SESSION sql_mode =
+					REPLACE(REPLACE(REPLACE(REPLACE(REPLACE(REPLACE(
+					@@sql_mode,
+					"STRICT_ALL_TABLES,", ""),
+					",STRICT_ALL_TABLES", ""),
+					"STRICT_ALL_TABLES", ""),
+					"STRICT_TRANS_TABLES,", ""),
+					",STRICT_TRANS_TABLES", ""),
+					"STRICT_TRANS_TABLES", "")'
+				);
+			}
 		}
 
 		if (is_array($this->encrypt))