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/mitchellh/go-wordwrap/LICENSE.md

@@ -0,0 +1,21 @@
+The MIT License (MIT)
+
+Copyright (c) 2014 Mitchell Hashimoto
+
+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/mitchellh/go-wordwrap/README.md

@@ -0,0 +1,39 @@
+# go-wordwrap
+
+`go-wordwrap` (Golang package: `wordwrap`) is a package for Go that
+automatically wraps words into multiple lines. The primary use case for this
+is in formatting CLI output, but of course word wrapping is a generally useful
+thing to do.
+
+## Installation and Usage
+
+Install using `go get github.com/mitchellh/go-wordwrap`.
+
+Full documentation is available at
+http://godoc.org/github.com/mitchellh/go-wordwrap
+
+Below is an example of its usage ignoring errors:
+
+```go
+wrapped := wordwrap.WrapString("foo bar baz", 3)
+fmt.Println(wrapped)
+```
+
+Would output:
+
+```
+foo
+bar
+baz
+```
+
+## Word Wrap Algorithm
+
+This library doesn't use any clever algorithm for word wrapping. The wrapping
+is actually very naive: whenever there is whitespace or an explicit linebreak.
+The goal of this library is for word wrapping CLI output, so the input is
+typically pretty well controlled human language. Because of this, the naive
+approach typically works just fine.
+
+In the future, we'd like to make the algorithm more advanced. We would do
+so without breaking the API.

vendor/github.com/mitchellh/go-wordwrap/wordwrap.go

@@ -0,0 +1,73 @@
+package wordwrap
+
+import (
+	"bytes"
+	"unicode"
+)
+
+// WrapString wraps the given string within lim width in characters.
+//
+// Wrapping is currently naive and only happens at white-space. A future
+// version of the library will implement smarter wrapping. This means that
+// pathological cases can dramatically reach past the limit, such as a very
+// long word.
+func WrapString(s string, lim uint) string {
+	// Initialize a buffer with a slightly larger size to account for breaks
+	init := make([]byte, 0, len(s))
+	buf := bytes.NewBuffer(init)
+
+	var current uint
+	var wordBuf, spaceBuf bytes.Buffer
+
+	for _, char := range s {
+		if char == '\n' {
+			if wordBuf.Len() == 0 {
+				if current+uint(spaceBuf.Len()) > lim {
+					current = 0
+				} else {
+					current += uint(spaceBuf.Len())
+					spaceBuf.WriteTo(buf)
+				}
+				spaceBuf.Reset()
+			} else {
+				current += uint(spaceBuf.Len() + wordBuf.Len())
+				spaceBuf.WriteTo(buf)
+				spaceBuf.Reset()
+				wordBuf.WriteTo(buf)
+				wordBuf.Reset()
+			}
+			buf.WriteRune(char)
+			current = 0
+		} else if unicode.IsSpace(char) {
+			if spaceBuf.Len() == 0 || wordBuf.Len() > 0 {
+				current += uint(spaceBuf.Len() + wordBuf.Len())
+				spaceBuf.WriteTo(buf)
+				spaceBuf.Reset()
+				wordBuf.WriteTo(buf)
+				wordBuf.Reset()
+			}
+
+			spaceBuf.WriteRune(char)
+		} else {
+
+			wordBuf.WriteRune(char)
+
+			if current+uint(spaceBuf.Len()+wordBuf.Len()) > lim && uint(wordBuf.Len()) < lim {
+				buf.WriteRune('\n')
+				current = 0
+				spaceBuf.Reset()
+			}
+		}
+	}
+
+	if wordBuf.Len() == 0 {
+		if current+uint(spaceBuf.Len()) <= lim {
+			spaceBuf.WriteTo(buf)
+		}
+	} else {
+		spaceBuf.WriteTo(buf)
+		wordBuf.WriteTo(buf)
+	}
+
+	return buf.String()
+}