kconfig: nconfig: fix multi-byte UTF handling

Currently, Kconfig descriptions that use multi-byte UTF-8 characters
(such as MTD_NAND_CAFE) will have their menu entries dropped from the
'make nconfig' ncurses menu, and all subsequent entries in the same
window will be omitted. This seems to be due to the ncurses 'menu'
library, which does not traditionally handle UTF-8 >8-bit characters
properly.

The ncursesw library ('w' is for "wide") is written to handle these
UTF-8 characters, and is practically a drop-in replacement at the source
level. Use it by default, if available.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=43067


Signed-off-by: Brian Norris <computersforpeace@gmail.com>
Cc: "Yann E. MORIN" <yann.morin.1998@free.fr>
Cc: Martin Walch <walch.martin@web.de>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Michal Marek <mmarek@suse.cz>