[llgo] Roll gotools to d4e70101.

[pcc]

Summary

Most importantly, this gives us https://go-review.googlesource.com/7533 which
fixes a bug in go/ssa that caused test failures in the Go 1.4 standard library.

Also remove the go1.4 tag workaround. We no longer need it now that we
ship llgo-go.

[axw]

LGTM

irgen/compiler.go

func (compiler *compiler) compile(fset *token.FileSet, astFiles []*ast.File, importpath string) (m *Module, err error) {
   impcfg := &loader.Config{
     Fset: fset,
     TypeChecker: types.Config{
       Packages: compiler.Packages,
       Import:   compiler.Importer,
       Sizes:    compiler.llvmtypes,
       DisableUnusedImportCheck: compiler.DisableUnusedImportCheck,
     },
-    Build:          &buildctx.Context,
-    PackageCreated: compiler.PackageCreated,
+    ImportFromBinary: true,
+    Build:            &buildctx.Context,
+    PackageCreated:   compiler.PackageCreated,
   }
   // If no import path is specified, then set the import
   // path to be the same as the package's name.
   if importpath == "" {
     importpath = astFiles[0].Name.String()
   }
   impcfg.CreateFromFiles(importpath, astFiles...)
   iprog, err := impcfg.Load()

update_third_party.sh

 #!/bin/sh -e
 
 gofrontendrepo=https://code.google.com/p/gofrontend
 gofrontendrev=0fde0b6a7eb2
 
 gccrepo=svn://gcc.gnu.org/svn/gcc/trunk
 gccrev=216268
 
 gotoolsrepo=https://go.googlesource.com/tools
-gotoolsrev=47f2109c640e97025f36c98610bd9782e815012e
+gotoolsrev=d4e70101500b43ffe705d4c45e50dd4f1c8e3b2e
 
 tempdir=$(mktemp -d /tmp/update_third_party.XXXXXX)
 gofrontenddir=$tempdir/gofrontend
 gotoolsdir=$tempdir/go.tools
 
 rm -rf third_party
 mkdir -p third_party/gofrontend third_party/gotools
 

 (cd $gotoolsdir && git checkout $gotoolsrev)
 
 cp -r $gotoolsdir/LICENSE $gotoolsdir/go third_party/gotools
 
 # Vendor the go.tools repository.
 find third_party/gotools -name '*.go' | xargs sed -i -e \
   's,"golang.org/x/tools/,"llvm.org/llgo/third_party/gotools/,g'
 
-# Until the version skew between the "go" tool and the compiler is resolved,
-# we patch out Go 1.4 specific code in go.tools.
-sed -i -e '/go1\.4/ d' third_party/gotools/go/exact/go13.go
-rm third_party/gotools/go/exact/go14.go
-
 # --------------------- license check ---------------------
 
 # We don't want any GPL licensed code without an autoconf/libtool
 # exception, or any GPLv3 licensed code.
 
 for i in `grep -lr 'General Public License' third_party` ; do
   if grep -q 'configuration script generated by Autoconf, you may include it under' $i || \
      grep -q 'is built using GNU Libtool, you may include this file under the' $i ; then