Bug#715261: manpages-dev: readdir_r should be strongly discouraged due to security reasons

[Michael Kerrisk (man-pages)]

tags 715261 fixed-upstream
thanks

glibc 2.24 marks readdir_r() deprecated, and for the upcoming
man-pages-4.05 release, I've significantly reworked the man page to
note the problems and indicate that the function is deprecated.

Thanks,

Michael