libyui-ncurses: Pass -DNCURSES_WIDECHAR in CXXFLAGS

We want the wide character functions from the ncurses header.
Unfortunately it doesn't provide them by default, but only
if either:
 * NCURSES_WIDECHAR is defined (for ncurses 20111030 and up)
 * _XOPEN_SOURCE/_XOPEN_SOURCE_EXTENDED are suitably defined

So far we have been implicitly relying on the latter, because
for GNU libc when we define _GNU_SOURCE this causes libc
to define the _XOPEN_SOURCE macros for us. Unfortunately
this doesn't work on all libcs, because some (like musl libc)
do not define _XOPEN_SOURCE when _GNU_SOURCE is defined.

Signed-off-by: Khem Raj <raj.khem@gmail.com>

meta-oe/recipes-graphics/libyui/libyui-ncurses_4.0.0.bb

@@ -21,6 +21,8 @@ BBCLASSEXTEND = "nativesdk"
 
 EXTRA_OECMAKE += "-DCMAKE_BUILD_TYPE=RELWITHDEBINFO -DWERROR=OFF"
 
+CXXFLAGS += "-DNCURSES_WIDECHAR"
+
 do_configure_prepend () {
     cd ${S}
     if [ -e ${PKG_CONFIG_SYSROOT_DIR}${base_prefix}/usr/lib/libyui.so ]; then