[dev.cc] cmd/internal/obj: reconvert from liblink

cmd/internal/obj reconverted using rsc.io/c2go rev 2a95256.

- Brings in new, more regular Prog, Addr definitions

- Add Prog* argument to oclass in liblink/asm[68].c, for c2go conversion.
- Update objwriter for change in TEXT size encoding.
- Merge 5a, 6a, 8a, 9a changes into new5a, new6a, new8a, new9a (by hand).

- Add +build ignore to cmd/asm/internal/{addr,arch,asm}, cmd/asm.
  They need to be updated for the changes.

- Reenable verifyAsm in cmd/go.
- Reenable GOOBJ=2 mode by default in liblink.

All architectures build successfully again.

Change-Id: I2c845c5d365aa484b570476898171bee657b626d
Reviewed-on: https://go-review.googlesource.com/3963
Reviewed-by: Rob Pike <r@golang.org>

src/cmd/asm/main.go

@@ -1,3 +1,5 @@
+// +build ignore
+
 // Copyright 2014 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.