#12 bw-rs232speed_2.1.5 improved NMRA timing

[Bernd Wagner]

This patch implements an additional value for the DDL configuration setting <improve_nmradcc_timing> (see man 5 srcpd.conf).

termios2 is an alternative method in linux to set a non-standard baudrate if the hardware supports it. In contrast to yes it supports newer linux kernels as well. With this method, the baudrate can be set by the nmradcc_baudrate parameter. This setting is hardware-dependent as well as the resulting real baudrate. (On a Raspberry Pi with baud base 3000000 more granular baudrates can be got by division than with the preset baud base 115200 of a standard PC's UART 16550A.)