Change tty default baud rate: 38400 -> 0, i.e. keep kernel default

This is a more sane default, and also what systems expect, and what
other getty implementations support.  I.e., unless specified, or set
to 0, the tty baud rate is zero -- which means do not change speed
at all.

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>

src/stty.c

@@ -27,6 +27,7 @@
 #include <sys/ttydefaults.h>  /* Not included by default in musl libc */
 #include <termios.h>
 
+/* B0 means; keep kernel default */
 speed_t stty_parse_speed(char *baud)
 {
 	char *ptr;
@@ -66,6 +67,9 @@ speed_t stty_parse_speed(char *baud)
 		{ 4000000, B4000000 },
 	};
 
+	if (!baud || !baud[0])
+		return B0;
+
 	errno = 0;
 	val = strtoul(baud, &ptr, 10);
 	if (errno || ptr == baud)