This is possible now that we no longer support go1.12 and brings
rclone into line with standard practices in the Go world.
This also removes errors.New and errors.Errorf from lib/errors and
prefers the stdlib errors package over lib/errors.
This patch modifies the output of `rclone version`.
The `os/arch` line is split into `os/type` and `os/arch`.
The `go version` line is now tagged as `go/version` for consistency.
Additionally the `go/linking` line tells whether the rclone
was linked as a static or dynamic executable.
The new `go/tags` line shows a space separated list of build tags.
The info about linking and build tags is also added to the output
of the `core/version` RC endpoint.
