Handle \r\n in gdbreplay

I tried gdbreplay yesterday, but the remotelogfile I received was made
on Windows, so the lines were terminated with \r\n rather than plain
\n.

This patch changes gdbreplay to allow \r\n line termination when
reading the log file.

gdb/gdbserver/ChangeLog
2019-02-27  Tom Tromey  <tromey@adacore.com>

	* gdbreplay.c (logchar): Handle \r\n.