posix: "fix" close-on-exec mode setting
posix: "fix" close-on-exec mode setting

Coverity and POSIX want you to get-and-set the file descriptor flags
(even though they are always zero by default).

Also drop fallback for Linux 2.6.26 and older.

xkfz007/vlc,xkfz007/vlc,xkfz007/vlc,xkfz007/vlc,xkfz007/vlc,xkfz007/vlc,xkfz007/vlc