build: scripts/config - update to kconfig-v5.6

Major changes include:
 - Much more readable reverse dependencies separated in groups
 - Improved recursive dependency report
 - More readable .config files: add comments to signal end of menus
 - More warnings for incorrect Config.in entries, such as a 'choice'
   default not contained in the 'choice'
 - Hability to properly display pseudographics with non-latin locales
 - Recursive dependencies can optionally be treated as errors

Changes from failed dcf3e63a35 attempt:
 - Recursive dependencies are treated as warnings by default
 - The option to treat them as errors is implemented as a command-line
   flag to scripts/config/conf instead of a compile-time definition
 - fixed handling of select with umnet dependencies

Cc: Petr Štetiar <ynezz@true.cz>
Cc: Jo-Philip Wich <jow@mein.io>
Signed-off-by: Eneas U de Queiroz <cotequeiroz@gmail.com>

scripts/config/mconf-cfg.sh

@@ -0,0 +1,50 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0
+
+PKG="ncursesw"
+PKG2="ncurses"
+
+if [ -n "$(command -v pkg-config)" ]; then
+	if pkg-config --exists $PKG; then
+		echo cflags=\"$(pkg-config --cflags $PKG)\"
+		echo libs=\"$(pkg-config --libs $PKG)\"
+		exit 0
+	fi
+
+	if pkg-config --exists $PKG2; then
+		echo cflags=\"$(pkg-config --cflags $PKG2)\"
+		echo libs=\"$(pkg-config --libs $PKG2)\"
+		exit 0
+	fi
+fi
+
+# Check the default paths in case pkg-config is not installed.
+# (Even if it is installed, some distributions such as openSUSE cannot
+# find ncurses by pkg-config.)
+if [ -f /usr/include/ncursesw/ncurses.h ]; then
+	echo cflags=\"-D_GNU_SOURCE -I/usr/include/ncursesw\"
+	echo libs=\"-lncursesw\"
+	exit 0
+fi
+
+if [ -f /usr/include/ncurses/ncurses.h ]; then
+	echo cflags=\"-D_GNU_SOURCE -I/usr/include/ncurses\"
+	echo libs=\"-lncurses\"
+	exit 0
+fi
+
+if [ -f /usr/include/ncurses.h ]; then
+	echo cflags=\"-D_GNU_SOURCE\"
+	echo libs=\"-lncurses\"
+	exit 0
+fi
+
+echo >&2 "*"
+echo >&2 "* Unable to find the ncurses package."
+echo >&2 "* Install ncurses (ncurses-devel or libncurses-dev"
+echo >&2 "* depending on your distribution)."
+echo >&2 "*"
+echo >&2 "* You may also need to install pkg-config to find the"
+echo >&2 "* ncurses installed in a non-default location."
+echo >&2 "*"
+exit 1