menuconfig: fix extended colors ncurses support

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.

Signed-off-by: Krzysztof Mazur <krzysiek@podlesie.net>
Signed-off-by: Michal Marek <mmarek@suse.cz>