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.

1 files changed, 105 insertions, 0 deletions

diff --git a/vendor/github.com/syndtr/goleveldb/README.md b/vendor/github.com/syndtr/goleveldb/README.md
new file mode 100644
index 000000000..259286f55
--- /dev/null
+++ b/vendor/github.com/syndtr/goleveldb/README.md
@@ -0,0 +1,105 @@
+This is an implementation of the [LevelDB key/value database](http:code.google.com/p/leveldb) in the [Go programming language](http:golang.org).
+
+[![Build Status](https://travis-ci.org/syndtr/goleveldb.png?branch=master)](https://travis-ci.org/syndtr/goleveldb)
+
+Installation
+-----------
+
+	go get github.com/syndtr/goleveldb/leveldb
+
+Requirements
+-----------
+
+* Need at least `go1.4` or newer.
+
+Usage
+-----------
+
+Create or open a database:
+```go
+db, err := leveldb.OpenFile("path/to/db", nil)
+...
+defer db.Close()
+...
+```
+Read or modify the database content:
+```go
+// Remember that the contents of the returned slice should not be modified.
+data, err := db.Get([]byte("key"), nil)
+...
+err = db.Put([]byte("key"), []byte("value"), nil)
+...
+err = db.Delete([]byte("key"), nil)
+...
+```
+
+Iterate over database content:
+```go
+iter := db.NewIterator(nil, nil)
+for iter.Next() {
+	// Remember that the contents of the returned slice should not be modified, and
+	// only valid until the next call to Next.
+	key := iter.Key()
+	value := iter.Value()
+	...
+}
+iter.Release()
+err = iter.Error()
+...
+```
+Seek-then-Iterate:
+```go
+iter := db.NewIterator(nil, nil)
+for ok := iter.Seek(key); ok; ok = iter.Next() {
+	// Use key/value.
+	...
+}
+iter.Release()
+err = iter.Error()
+...
+```
+Iterate over subset of database content:
+```go
+iter := db.NewIterator(&util.Range{Start: []byte("foo"), Limit: []byte("xoo")}, nil)
+for iter.Next() {
+	// Use key/value.
+	...
+}
+iter.Release()
+err = iter.Error()
+...
+```
+Iterate over subset of database content with a particular prefix:
+```go
+iter := db.NewIterator(util.BytesPrefix([]byte("foo-")), nil)
+for iter.Next() {
+	// Use key/value.
+	...
+}
+iter.Release()
+err = iter.Error()
+...
+```
+Batch writes:
+```go
+batch := new(leveldb.Batch)
+batch.Put([]byte("foo"), []byte("value"))
+batch.Put([]byte("bar"), []byte("another value"))
+batch.Delete([]byte("baz"))
+err = db.Write(batch, nil)
+...
+```
+Use bloom filter:
+```go
+o := &opt.Options{
+	Filter: filter.NewBloomFilter(10),
+}
+db, err := leveldb.OpenFile("path/to/db", o)
+...
+defer db.Close()
+...
+```
+Documentation
+-----------
+
+You can read package documentation [here](http:godoc.org/github.com/syndtr/goleveldb).