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/rs/cors/README.md

@@ -0,0 +1,99 @@
+# Go CORS handler [![godoc](http://img.shields.io/badge/godoc-reference-blue.svg?style=flat)](https://godoc.org/github.com/rs/cors) [![license](http://img.shields.io/badge/license-MIT-red.svg?style=flat)](https://raw.githubusercontent.com/rs/cors/master/LICENSE) [![build](https://img.shields.io/travis/rs/cors.svg?style=flat)](https://travis-ci.org/rs/cors) [![Coverage](http://gocover.io/_badge/github.com/rs/cors)](http://gocover.io/github.com/rs/cors)
+
+CORS is a `net/http` handler implementing [Cross Origin Resource Sharing W3 specification](http://www.w3.org/TR/cors/) in Golang.
+
+## Getting Started
+
+After installing Go and setting up your [GOPATH](http://golang.org/doc/code.html#GOPATH), create your first `.go` file. We'll call it `server.go`.
+
+```go
+package main
+
+import (
+    "net/http"
+
+    "github.com/rs/cors"
+)
+
+func main() {
+    mux := http.NewServeMux()
+    mux.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
+        w.Header().Set("Content-Type", "application/json")
+        w.Write([]byte("{\"hello\": \"world\"}"))
+    })
+
+    // cors.Default() setup the middleware with default options being
+    // all origins accepted with simple methods (GET, POST). See
+    // documentation below for more options.
+    handler := cors.Default().Handler(mux)
+    http.ListenAndServe(":8080", handler)
+}
+```
+
+Install `cors`:
+
+    go get github.com/rs/cors
+
+Then run your server:
+
+    go run server.go
+
+The server now runs on `localhost:8080`:
+
+    $ curl -D - -H 'Origin: http://foo.com' http://localhost:8080/
+    HTTP/1.1 200 OK
+    Access-Control-Allow-Origin: foo.com
+    Content-Type: application/json
+    Date: Sat, 25 Oct 2014 03:43:57 GMT
+    Content-Length: 18
+
+    {"hello": "world"}
+
+### More Examples
+
+* `net/http`: [examples/nethttp/server.go](https://github.com/rs/cors/blob/master/examples/nethttp/server.go)
+* [Goji](https://goji.io): [examples/goji/server.go](https://github.com/rs/cors/blob/master/examples/goji/server.go)
+* [Martini](http://martini.codegangsta.io): [examples/martini/server.go](https://github.com/rs/cors/blob/master/examples/martini/server.go)
+* [Negroni](https://github.com/codegangsta/negroni): [examples/negroni/server.go](https://github.com/rs/cors/blob/master/examples/negroni/server.go)
+* [Alice](https://github.com/justinas/alice): [examples/alice/server.go](https://github.com/rs/cors/blob/master/examples/alice/server.go)
+
+## Parameters
+
+Parameters are passed to the middleware thru the `cors.New` method as follow:
+
+```go
+c := cors.New(cors.Options{
+    AllowedOrigins: []string{"http://foo.com"},
+    AllowCredentials: true,
+})
+
+// Insert the middleware
+handler = c.Handler(handler)
+```
+
+* **AllowedOrigins** `[]string`: A list of origins a cross-domain request can be executed from. If the special `*` value is present in the list, all origins will be allowed. An origin may contain a wildcard (`*`) to replace 0 or more characters (i.e.: `http://*.domain.com`). Usage of wildcards implies a small performance penality. Only one wildcard can be used per origin. The default value is `*`.
+* **AllowOriginFunc** `func (origin string) bool`: A custom function to validate the origin. It take the origin as argument and returns true if allowed or false otherwise. If this option is set, the content of `AllowedOrigins` is ignored
+* **AllowedMethods** `[]string`: A list of methods the client is allowed to use with cross-domain requests. Default value is simple methods (`GET` and `POST`).
+* **AllowedHeaders** `[]string`: A list of non simple headers the client is allowed to use with cross-domain requests.
+* **ExposedHeaders** `[]string`: Indicates which headers are safe to expose to the API of a CORS API specification
+* **AllowCredentials** `bool`: Indicates whether the request can include user credentials like cookies, HTTP authentication or client side SSL certificates. The default is `false`.
+* **MaxAge** `int`: Indicates how long (in seconds) the results of a preflight request can be cached. The default is `0` which stands for no max age.
+* **OptionsPassthrough** `bool`: Instructs preflight to let other potential next handlers to process the `OPTIONS` method. Turn this on if your application handles `OPTIONS`.
+* **Debug** `bool`: Debugging flag adds additional output to debug server side CORS issues.
+
+See [API documentation](http://godoc.org/github.com/rs/cors) for more info.
+
+## Benchmarks
+
+    BenchmarkWithout          20000000    64.6 ns/op      8 B/op    1 allocs/op
+    BenchmarkDefault          3000000      469 ns/op    114 B/op    2 allocs/op
+    BenchmarkAllowedOrigin    3000000      608 ns/op    114 B/op    2 allocs/op
+    BenchmarkPreflight        20000000    73.2 ns/op      0 B/op    0 allocs/op
+    BenchmarkPreflightHeader  20000000    73.6 ns/op      0 B/op    0 allocs/op
+    BenchmarkParseHeaderList  2000000      847 ns/op    184 B/op    6 allocs/op
+    BenchmarkParse…Single     5000000      290 ns/op     32 B/op    3 allocs/op
+    BenchmarkParse…Normalized 2000000      776 ns/op    160 B/op    6 allocs/op
+
+## Licenses
+
+All source code is licensed under the [MIT License](https://raw.github.com/rs/cors/master/LICENSE).