[FFmpeg-cvslog] configure: define posix source on cygwin

[Timo Rothenpieler]

ffmpeg | branch: master | Timo Rothenpieler <timo at rothenpieler.org> | Fri Sep 30 12:17:16 2016 +0200| [b7bd5b9794223f12203142159a22b176da2378e8] | committer: Timo Rothenpieler

configure: define posix source on cygwin

Some function definitions are missing without it,
for example sigaction.

Fixes ticket #5868

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=b7bd5b9794223f12203142159a22b176da2378e8
---

 configure | 1 +
 1 file changed, 1 insertion(+)

diff --git a/configure b/configure
index df6ffa2..2b141fb 100755
--- a/configure
+++ b/configure
@@ -4802,6 +4802,7 @@ case $target_os in
         objformat="win32"
         enable dos_paths
         enabled shared && ! enabled small && check_cmd $windres --version && enable gnu_windres
+        add_cppflags -D_POSIX_C_SOURCE=200112 -D_XOPEN_SOURCE=600
         ;;
     *-dos|freedos|opendos)
         network_extralibs="-lsocket"