[RFC] Golang fixes

With https://github.com/flycheck/flycheck/pull/107 support for golang was added, with the minor issue that output to /dev/null didn't work in some cases. An upstream ticket was filed (https://code.google.com/p/go/issues/detail?id=4851) and all was good. Today the upstream ticket is closed with something along the lines "won't fix" and therefore some other solution should be found.

I added a temporary file mechanism which resolves the "build output ... exists" problem. But some problems with errors related to missing packages or errors inside of dependent packages remain. I added test cases that try to document these problems.

As my elisp knowledge is limited/not existing I can't come up with a proper solution for myself and request your comments.