go 1.1

Removes the now-outdated devel block.

Also require the use of the correct clang compiler
by default. This change was needed when using
--devel and now needed in stable.

A new caveat has also been added explaining how a
$GOPATH must be set and cannot be the same as
$GOROOT From the 1.1 release notes listed below.
http://golang.org/doc/go1.1#gocmd

Closes #19782.

Signed-off-by: Misty De Meo <mistydemeo@gmail.com>