scripts/kconfig/mconf.c: survive is SIGWINCH is not defined

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/scripts/kconfig/mconf.c b/scripts/kconfig/mconf.c
index 006d037..adba114 100644
--- a/scripts/kconfig/mconf.c
+++ b/scripts/kconfig/mconf.c
@@ -27,6 +27,10 @@
 #include <unistd.h>
 #include <locale.h>
 
+#ifndef SIGWINCH
+#define SIGWINCH 28
+#endif
+
 #define LKC_DIRECT_LINK
 #include "lkc.h"