nginx: security bump to version 1.12.1

nginx: security bump to version 1.12.1

Fixes CVE-2017-7529 - Nginx versions since 0.5.6 up to and including 1.13.2
are vulnerable to integer overflow vulnerability in nginx range filter
module resulting into leak of potentially sensitive information triggered by
specially crafted request.

For more details, see:
http://mailman.nginx.org/pipermail/nginx-announce/2017/000200.html

Signed-off-by: Peter Korsgaard <peter@korsgaard.com>