ncurses, cmus, and _POSIX_C_SOURCE

[Tobias Kortkamp]

Hi,

I've got a report where audio/cmus will fail to build with ncurses from
ports (https://bugs.freebsd.org/214475).  The trouble seems to come from
ncurses' pkgconf file with adds -D_POSIX_C_SOURCE=200112L to CFLAGS
which hides strndup (which is available with _POSIX_C_SOURCE >= 200809)
from cmus.  I can "fix" the cmus build by adding a prototype for
strndup, but I'm wondering if devel/ncurses may be doing something wrong
here by defining _POSIX_C_SOURCE like it does?

Thanks!