lib/Tools/gofmt

added proof method "iprover" to try0

#!/usr/bin/env bash
#
# Author: Makarius
#
# DESCRIPTION: invoke gofmt within the Isabelle environment

if [ -z "$ISABELLE_GOEXE" ]; then
  echo "Missing Go installation: need to run \"isabelle go_setup\" first" >&2
  exit 2
else
  export GOROOT="$(platform_path "$ISABELLE_GOROOT")"
  exec "$ISABELLE_GOEXE/gofmt" "$@"
fi