Update go to 1.7.5 in stable
The go package in stable runs 1.7.3. 1.7.5 is the latest version of the
1.7 release and contains both important bug fixes to cross compile, and
two security fixes in 1.7.4.
https://golang.org/doc/devel/release.html\#go1.7.minor
(from redmine: issue id 7124, created on 2017-04-12)