[ticket/16051] Remove mysql driver as it's no longer supported in PHP >= 7.0

PHPBB3-16051

phpBB/includes/acp/acp_database.php

@@ -248,8 +248,6 @@ class acp_database
 
 							switch ($db->get_sql_layer())
 							{
-								case 'mysql':
-								case 'mysql4':
 								case 'mysqli':
 								case 'sqlite3':
 									while (($sql = $fgetd($fp, ";\n", $read, $seek, $eof)) !== false)

phpBB/includes/acp/acp_forums.php

@@ -1878,7 +1878,6 @@ class acp_forums
 
 		switch ($db->get_sql_layer())
 		{
-			case 'mysql4':
 			case 'mysqli':
 
 				// Delete everything else and thank MySQL for offering multi-table deletion

phpBB/includes/acp/acp_reasons.php

@@ -222,8 +222,6 @@ class acp_reasons
 					{
 						// The ugly one!
 						case 'mysqli':
-						case 'mysql4':
-						case 'mysql':
 							// Change the reports using this reason to 'other'
 							$sql = 'UPDATE ' . REPORTS_TABLE . '
 								SET reason_id = ' . $other_reason_id . ", report_text = CONCAT('" . $db->sql_escape($reason_row['reason_description']) . "\n\n', report_text)