configure: fixup extended colors in wide-char-enabled ncurses

configure: fixup extended colors in wide-char-enabled ncurses

As Krzysztof puts it in its commit log in the Linux kernel:

    The ncurses library allows for extended colors. The support for extended
    colors support depends on wide-character support. ncurses headers
    enable extended colors (NCURSES_EXT_COLORS) only when wide-character
    support is enabled (NCURSES_WIDECHAR).

    The "make menuconfig" uses wide-character ncursesw library, which can be
    compiled with wide-character support, but does not define NCURSES_WIDECHAR
    and it's using headers without wide-character (and extended colors) support.

    This fixes problems with colors on systems with enabled extended colors
    (like PLD Linux). Without this patch "make menuconfig" is hard to use.

In kconfig-frontends, we fix this by adding the appropriate CPPFLAGS to the
mconf-specific ncurses CPPFLAGS.

Reported-by: Krzysztof Mazur <krzysiek@podlesie.net>
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>