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>
18e92f2c6c