Change serial_send_break and serial_write to throw

Change serial_send_break and serial_write to throw

This changes serial_send_break and serial_write to throw exceptions
rather than attempt to set errno and return an error indicator.  This
lets us correctly report failures on Windows.

Both functions had to be converted in a single patch because one
implementation of send_break works via write.

This also introduces remote_serial_send_break to handle error checking
when attempting to send a break.  This was previously ignored.

Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=30770