Correctly handle /usr/gnu/bin/stty sane on Solaris.
This problem has been fixed upstream.
See:
--- src/stty.c.orig 2016-06-28 17:48:25.580754994 -0700
+++ src/stty.c 2016-06-29 06:19:49.159950703 -0700
@@ -118,9 +118,9 @@
# define CSWTCH _POSIX_VDISABLE
#endif
-/* SunOS 5.3 loses (^Z doesn't work) if 'swtch' is the same as 'susp'.
+/* SunOS >= 5.3 loses (^Z doesn't work) if 'swtch' is the same as 'susp'.
So the default is to disable 'swtch.' */
-#if defined __sparc__ && defined __svr4__
+#if defined __sun
# undef CSWTCH
# define CSWTCH _POSIX_VDISABLE
#endif