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/gopkg.in/check.v1/printer.go

@@ -0,0 +1,168 @@
+package check
+
+import (
+	"bytes"
+	"go/ast"
+	"go/parser"
+	"go/printer"
+	"go/token"
+	"os"
+)
+
+func indent(s, with string) (r string) {
+	eol := true
+	for i := 0; i != len(s); i++ {
+		c := s[i]
+		switch {
+		case eol && c == '\n' || c == '\r':
+		case c == '\n' || c == '\r':
+			eol = true
+		case eol:
+			eol = false
+			s = s[:i] + with + s[i:]
+			i += len(with)
+		}
+	}
+	return s
+}
+
+func printLine(filename string, line int) (string, error) {
+	fset := token.NewFileSet()
+	file, err := os.Open(filename)
+	if err != nil {
+		return "", err
+	}
+	fnode, err := parser.ParseFile(fset, filename, file, parser.ParseComments)
+	if err != nil {
+		return "", err
+	}
+	config := &printer.Config{Mode: printer.UseSpaces, Tabwidth: 4}
+	lp := &linePrinter{fset: fset, fnode: fnode, line: line, config: config}
+	ast.Walk(lp, fnode)
+	result := lp.output.Bytes()
+	// Comments leave \n at the end.
+	n := len(result)
+	for n > 0 && result[n-1] == '\n' {
+		n--
+	}
+	return string(result[:n]), nil
+}
+
+type linePrinter struct {
+	config *printer.Config
+	fset   *token.FileSet
+	fnode  *ast.File
+	line   int
+	output bytes.Buffer
+	stmt   ast.Stmt
+}
+
+func (lp *linePrinter) emit() bool {
+	if lp.stmt != nil {
+		lp.trim(lp.stmt)
+		lp.printWithComments(lp.stmt)
+		lp.stmt = nil
+		return true
+	}
+	return false
+}
+
+func (lp *linePrinter) printWithComments(n ast.Node) {
+	nfirst := lp.fset.Position(n.Pos()).Line
+	nlast := lp.fset.Position(n.End()).Line
+	for _, g := range lp.fnode.Comments {
+		cfirst := lp.fset.Position(g.Pos()).Line
+		clast := lp.fset.Position(g.End()).Line
+		if clast == nfirst-1 && lp.fset.Position(n.Pos()).Column == lp.fset.Position(g.Pos()).Column {
+			for _, c := range g.List {
+				lp.output.WriteString(c.Text)
+				lp.output.WriteByte('\n')
+			}
+		}
+		if cfirst >= nfirst && cfirst <= nlast && n.End() <= g.List[0].Slash {
+			// The printer will not include the comment if it starts past
+			// the node itself. Trick it into printing by overlapping the
+			// slash with the end of the statement.
+			g.List[0].Slash = n.End() - 1
+		}
+	}
+	node := &printer.CommentedNode{n, lp.fnode.Comments}
+	lp.config.Fprint(&lp.output, lp.fset, node)
+}
+
+func (lp *linePrinter) Visit(n ast.Node) (w ast.Visitor) {
+	if n == nil {
+		if lp.output.Len() == 0 {
+			lp.emit()
+		}
+		return nil
+	}
+	first := lp.fset.Position(n.Pos()).Line
+	last := lp.fset.Position(n.End()).Line
+	if first <= lp.line && last >= lp.line {
+		// Print the innermost statement containing the line.
+		if stmt, ok := n.(ast.Stmt); ok {
+			if _, ok := n.(*ast.BlockStmt); !ok {
+				lp.stmt = stmt
+			}
+		}
+		if first == lp.line && lp.emit() {
+			return nil
+		}
+		return lp
+	}
+	return nil
+}
+
+func (lp *linePrinter) trim(n ast.Node) bool {
+	stmt, ok := n.(ast.Stmt)
+	if !ok {
+		return true
+	}
+	line := lp.fset.Position(n.Pos()).Line
+	if line != lp.line {
+		return false
+	}
+	switch stmt := stmt.(type) {
+	case *ast.IfStmt:
+		stmt.Body = lp.trimBlock(stmt.Body)
+	case *ast.SwitchStmt:
+		stmt.Body = lp.trimBlock(stmt.Body)
+	case *ast.TypeSwitchStmt:
+		stmt.Body = lp.trimBlock(stmt.Body)
+	case *ast.CaseClause:
+		stmt.Body = lp.trimList(stmt.Body)
+	case *ast.CommClause:
+		stmt.Body = lp.trimList(stmt.Body)
+	case *ast.BlockStmt:
+		stmt.List = lp.trimList(stmt.List)
+	}
+	return true
+}
+
+func (lp *linePrinter) trimBlock(stmt *ast.BlockStmt) *ast.BlockStmt {
+	if !lp.trim(stmt) {
+		return lp.emptyBlock(stmt)
+	}
+	stmt.Rbrace = stmt.Lbrace
+	return stmt
+}
+
+func (lp *linePrinter) trimList(stmts []ast.Stmt) []ast.Stmt {
+	for i := 0; i != len(stmts); i++ {
+		if !lp.trim(stmts[i]) {
+			stmts[i] = lp.emptyStmt(stmts[i])
+			break
+		}
+	}
+	return stmts
+}
+
+func (lp *linePrinter) emptyStmt(n ast.Node) *ast.ExprStmt {
+	return &ast.ExprStmt{&ast.Ellipsis{n.Pos(), nil}}
+}
+
+func (lp *linePrinter) emptyBlock(n ast.Node) *ast.BlockStmt {
+	p := n.Pos()
+	return &ast.BlockStmt{p, []ast.Stmt{lp.emptyStmt(n)}, p}
+}