kconfig: fix menuconfig on debian lenny

In 60f33b80 (kconfig: get rid of stray a.o, support ncursesw, 2006-01-15),
support to link menuconfig with ncursesw library was added.  To compute
the linker command option -l, we check "libncursesw.{so,a,dylib}" to allow
ncursesw to be used as a replacement ncurses.  However, when checking what
header file to include, we do not check /usr/include/ncursesw directory.

Add /usr/include/ncursesw to the list of directories that are checked.
With this patch, on my Debian Lenny box with libncursesw5-dev package but
not libncurses5-dev package, I can say "make menuconfig".

Signed-off-by: Junio C Hamano <gitster@pobox.com>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Michal Marek <mmarek@suse.cz>