Godeps, vendor: convert dependency management to trash (#3198)

This commit converts the dependency management from Godeps to the vendor
folder, also switching the tool from godep to trash. Since the upstream tool
lacks a few features proposed via a few PRs, until those PRs are merged in
(if), use github.com/karalabe/trash.

You can update dependencies via trash --update.

All dependencies have been updated to their latest version.

Parts of the build system are reworked to drop old notions of Godeps and
invocation of the go vet command so that it doesn't run against the vendor
folder, as that will just blow up during vetting.

The conversion drops OpenCL (and hence GPU mining support) from ethash and our
codebase. The short reasoning is that there's noone to maintain and having
opencl libs in our deps messes up builds as go install ./... tries to build
them, failing with unsatisfied link errors for the C OpenCL deps.

golang.org/x/net/context is not vendored in. We expect it to be fetched by the
user (i.e. using go get). To keep ci.go builds reproducible the package is
"vendored" in build/_vendor.

vendor/github.com/cespare/cp/LICENSE.txt

@@ -0,0 +1,19 @@
+Copyright (c) 2015 Caleb Spare
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.

vendor/github.com/cespare/cp/README.md

@@ -0,0 +1,9 @@
+# cp
+
+[![GoDoc](https://godoc.org/github.com/cespare/cp?status.svg)](https://godoc.org/github.com/cespare/cp)
+
+cp is a small Go package for copying files and directories.
+
+The API may change because I want to add some options in the future (for merging with existing dirs).
+
+It does not currently handle Windows specifically (I think it may require some special treatment).

vendor/github.com/cespare/cp/cp.go

@@ -0,0 +1,58 @@
+// Package cp offers simple file and directory copying for Go.
+package cp
+
+import (
+	"errors"
+	"io"
+	"os"
+	"path/filepath"
+	"strings"
+)
+
+var errCopyFileWithDir = errors.New("dir argument to CopyFile")
+
+// CopyFile copies the file with path src to dst. The new file must not exist.
+// It is created with the same permissions as src.
+func CopyFile(dst, src string) error {
+	rf, err := os.Open(src)
+	if err != nil {
+		return err
+	}
+	defer rf.Close()
+	rstat, err := rf.Stat()
+	if err != nil {
+		return err
+	}
+	if rstat.IsDir() {
+		return errCopyFileWithDir
+	}
+
+	wf, err := os.OpenFile(dst, os.O_WRONLY|os.O_CREATE|os.O_EXCL, rstat.Mode())
+	if err != nil {
+		return err
+	}
+	if _, err := io.Copy(wf, rf); err != nil {
+		wf.Close()
+		return err
+	}
+	return wf.Close()
+}
+
+// CopyAll copies the file or (recursively) the directory at src to dst.
+// Permissions are preserved. dst must not already exist.
+func CopyAll(dst, src string) error {
+	return filepath.Walk(src, makeWalkFn(dst, src))
+}
+
+func makeWalkFn(dst, src string) filepath.WalkFunc {
+	return func(path string, info os.FileInfo, err error) error {
+		if err != nil {
+			return err
+		}
+		dstPath := filepath.Join(dst, strings.TrimPrefix(path, src))
+		if info.IsDir() {
+			return os.Mkdir(dstPath, info.Mode())
+		}
+		return CopyFile(dstPath, path)
+	}
+}