Update used Go version to 1.3.

Go downloads moved to a different URL and require following redirects
(curl's '-L' option) now.

Go 1.3 deliberately randomizes ranges over maps, which uncovered some
bugs in our tests. These are fixed too.

Change-Id: Id2d9e185d8d2379a9b7b8ad5ba680024565d15f4
Merge "Update used Go version to 1.3."