Fix [-Wimplicit-fallthrough] warnings in MySQLnd extension

Author: Girgias

ext/mysqlnd/mysqlnd_connection.c

@@ -1254,7 +1254,7 @@ MYSQLND_METHOD(mysqlnd_conn_data, send_close)(MYSQLND_CONN_DATA * const conn)
 			  Do nothing, the connection will be brutally closed
 			  and the server will catch it and free close from its side.
 			*/
-			/* Fall-through */
+			fallthrough;
 		case CONN_ALLOCED:
 			/*
 			  Allocated but not connected or there was failure when trying
@@ -1263,7 +1263,7 @@ MYSQLND_METHOD(mysqlnd_conn_data, send_close)(MYSQLND_CONN_DATA * const conn)
 			  Fall-through
 			*/
 			SET_CONNECTION_STATE(&conn->state, CONN_QUIT_SENT);
-			/* Fall-through */
+			fallthrough;
 		case CONN_QUIT_SENT:
 			/* The user has killed its own connection */
 			vio->data->m.close_stream(vio, conn->stats, conn->error_info);

ext/mysqlnd/mysqlnd_debug.c

@@ -515,6 +515,7 @@ MYSQLND_METHOD(mysqlnd_debug, set_mode)(MYSQLND_DEBUG * self, const char * const
 			case 'O':
 			case 'A':
 				self->flags |= MYSQLND_DEBUG_FLUSH;
+				fallthrough;
 			case 'a':
 			case 'o':
 				if (mode[i] == 'a' || mode[i] == 'A') {

ext/mysqlnd/mysqlnd_ps_codec.c

@@ -742,7 +742,7 @@ mysqlnd_stmt_execute_calculate_param_values_size(MYSQLND_STMT_DATA * stmt, zval
 				break;
 			case MYSQL_TYPE_LONGLONG:
 				is_longlong = 4;
-				/* fall-through */
+				fallthrough;
 			case MYSQL_TYPE_LONG:
 				{
 					zval *tmp_data = (*copies_param && !Z_ISUNDEF((*copies_param)[i]))? &(*copies_param)[i]: the_var;