kconfig: if ncurses-devel is missing then say so

With this patch when ncurses-devel (or whatever it is named)
is missing trying to run menuconfig will result in this:

$ make menuconfig
  HOSTCC  scripts/kconfig/conf.o
  HOSTCC  scripts/kconfig/kxgettext.o
 *** Unable to find the ncurses libraries or the
 *** required header files.
 *** 'make menuconfig' requires the ncurses libraries.
 ***
 *** Install ncurses (ncurses-devel) and try again.
 ***
make[1]: *** [scripts/kconfig/dochecklxdialog] Error 1
make: *** [menuconfig] Error 2

Much better than before where we just listed some build errors.
The other *config targets will work indepenednt on ncurses
being present or not.

Includes improvements suggested by: Frans Pop <elendil@planet.nl>

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Cc: Frans Pop <elendil@planet.nl>

scripts/kconfig/lxdialog/check-lxdialog.sh

@@ -36,14 +36,16 @@ trap "rm -f $tmp" 0 1 2 3 15
 
 # Check if we can link to ncurses
 check() {
-	echo "main() {}" | $cc -xc - -o $tmp 2> /dev/null
+	echo -e " #include CURSES_LOC \n main() {}" |
+	    $cc -xc - -o $tmp 2> /dev/null
 	if [ $? != 0 ]; then
-		echo " *** Unable to find the ncurses libraries."          1>&2
-		echo " *** make menuconfig require the ncurses libraries"  1>&2
-		echo " *** "                                               1>&2
-		echo " *** Install ncurses (ncurses-devel) and try again"  1>&2
-		echo " *** "                                               1>&2
-		exit 1
+	    echo " *** Unable to find the ncurses libraries or the"       1>&2
+	    echo " *** required header files."                            1>&2
+	    echo " *** 'make menuconfig' requires the ncurses libraries." 1>&2
+	    echo " *** "                                                  1>&2
+	    echo " *** Install ncurses (ncurses-devel) and try again."    1>&2
+	    echo " *** "                                                  1>&2
+	    exit 1
 	fi
 }