Log Message:
Add Go 1.11 as lang/go111.

This installs the go tool as go111; all the supporting files go under
$PREFIX/go111, so it does not conflict with other Go versions. Go packages
in pkgsrc do not use it to build yet.

Changes:

There are many changes and improvements to the toolchain, runtime, and
libraries, but two features stand out as being especially exciting: modules
and WebAssembly support.

This release adds preliminary support for a new concept called \ 
"modules," an
alternative to GOPATH with integrated support for versioning and package
distribution. Module support is considered experimental, and there are still
a few rough edges to smooth out, so please make liberal use of the issue
tracker.

Go 1.11 also adds an experimental port to WebAssembly (js/wasm). This allows
programmers to compile Go programs to a binary format compatible with four
major web browsers.