Fix build with musl by ensuring CTRL is defined.

musl does not define CTRL in <termios.h>, we could include <sys/ttydefaults.h>
explicitly but it's easier just to ensure CTRL is defined.

This patch is taken from Sabotage Linux, the license statement for patches and
build scripts in Sabotage Linux says:

    To the extent possible under law, Christian Neukirchen has waived
    all copyright and related or neighboring rights to this work.

    http://creativecommons.org/publicdomain/zero/1.0/

Therefore this should be good to include in OpenEmbedded.

Signed-off-by: Paul Barker <paul@paulbarker.me.uk>

Upstream-status: Accepted (should be included in v4.8.14)

diff -u mc-4.8.1.7.org/lib/tty/tty-ncurses.c mc-4.8.1.7/lib/tty/tty-ncurses.c
--- mc-4.8.1.7.org/lib/tty/tty-ncurses.c
+++ mc-4.8.1.7/lib/tty/tty-ncurses.c
@@ -65,7 +65,7 @@
 
 /*** file scope macro definitions ****************************************************************/
 
-#if defined(_AIX) && !defined(CTRL)
+#if !defined(CTRL)
 #define CTRL(x) ((x) & 0x1f)
 #endif
 
