Merge commit 'd06146ed970f52d564521ff0be7d56839c85e497' into async-functions

* commit 'd06146ed970f52d564521ff0be7d56839c85e497': (152 commits)
  perf(lib/sync): avoid using `defer`
  refactor(c-libuv): Added TODO(uid) comment & adjusted the position of Handle, Stream, Req, Write, Connect
  README: io/ioutil
  library: io/ioutil
  c/openssl: bio, pem, rsa
  refactor(c/libuv): Adapt libuv.Fs struct
  Revert "fix(c/libuv): Add libuv fs struct new func"
  fix(c/libuv): Fix async_fs demo return 255 error & pointer not allocated error
  fix(c/libuv): Add libuv fs struct new func
  doc/c:refine symbol visibility description
  README: math/big
  library: math/big.Int (mini-impl for _cmptest/bigintdemo)
  doc/c:update implicit destructors description
  c/openssl: bignum, rsa
  library: crypto
  library: crypto/{sha1, sha256, sha512}
  doc/c:fix incorrect usage in construtors
  doc/c:update destructor usage
  delete sum
  fix test error
  ...

# Conflicts:
#	ssa/eh.go

ssa/package.go

@@ -19,6 +19,7 @@ package ssa
 import (
 	"go/token"
 	"go/types"
+	"runtime"
 	"strconv"
 	"unsafe"
 
@@ -240,7 +241,10 @@ type Program = *aProgram
 // NewProgram creates a new program.
 func NewProgram(target *Target) Program {
 	if target == nil {
-		target = &Target{}
+		target = &Target{
+			GOOS:   runtime.GOOS,
+			GOARCH: runtime.GOARCH,
+		}
 	}
 	ctx := llvm.NewContext()
 	td := target.targetData() // TODO(xsw): target config
@@ -653,7 +657,7 @@ const (
 	closureStub = "__llgo_stub."
 )
 
-func (p Package) closureStub(b Builder, t *types.Struct, v Expr) Expr {
+func (p Package) closureStub(b Builder, t types.Type, v Expr) Expr {
 	name := v.impl.Name()
 	prog := b.Prog
 	nilVal := prog.Nil(prog.VoidPtr()).impl