kconfig: allow stdin/stdout redirection

Allow stdin/stdout redirection for the CLI conf (not mconf).
This allows to recall a sample and automatically apply the defaults
to new configuration option, with something like the following:
yes "" |ct-ng "sample_name"

 #!/bin/sh

 # Needed for systems without gettext

 $* -xc -o /dev/null - > /dev/null 2>&1 << EOF

 #include <libintl.h>

 int main()

 {

 	gettext("");

 	return 0;

 }

 EOF

 if [ ! "$?" -eq "0"  ]; then

 	echo -DKBUILD_NO_NLS;

 fi