gdb: unix: allow to use custom baud rate

Modern unix systems allow to set custom baud rate instead of predefined in termios.h.

- To use this in Linux it must have BOTHER macro in "asm/termio.h"
- MacOS could handle this using IOSSIOSPEED passed to ioctl()

Approved-By: Simon Marchi <simon.marchi@efficios.com>
Change-Id: I5bc95982f5d90c7030b73f484ecc0f75c060ebf7
4 files changed