imports: add unsafe symbols to zstdlib

Change-Id: Ia5856e2197925671ebaa5e673af3e97fad1cdaee
Reviewed-on: https://go-review.googlesource.com/24463
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

imports/mkstdlib.go

@@ -86,6 +86,10 @@ func main() {
 			outf("\t%q: %q,\n", key, fullImport[key])
 		}
 	}
+	outf("\n")
+	for _, sym := range [...]string{"Alignof", "ArbitraryType", "Offsetof", "Pointer", "Sizeof"} {
+		outf("\t%q: %q,\n", "unsafe."+sym, "unsafe")
+	}
 	outf("}\n")
 	fmtbuf, err := format.Source(buf.Bytes())
 	if err != nil {

imports/zstdlib.go

@@ -9153,4 +9153,10 @@ var stdlib = map[string]string{
 	"zlib.NoCompression":                          "compress/zlib",
 	"zlib.Resetter":                               "compress/zlib",
 	"zlib.Writer":                                 "compress/zlib",
+
+	"unsafe.Alignof":       "unsafe",
+	"unsafe.ArbitraryType": "unsafe",
+	"unsafe.Offsetof":      "unsafe",
+	"unsafe.Pointer":       "unsafe",
+	"unsafe.Sizeof":        "unsafe",
 }