glibc: patch CVE-2015-7547

The glibc DNS client side resolver is vulnerable to a stack-based buffer
overflow when the getaddrinfo() library function is used. Software using
this function may be exploited with attacker-controlled domain names,
attacker-controlled DNS servers, or through a man-in-the-middle attack.
https://googleonlinesecurity.blogspot.co.uk/2016/02/cve-2015-7547-glibc-getaddrinfo-stack.html