runtime: delete runtime/internal/atomic/textflag.h

As per mdempsky's comment on golang.org/cl/14204, textflag.h is
copied to the includes dir by cmd/dist, and the copy in
runtime/internal/atomic is not actually being used.

Updates #11647

Change-Id: Ie95c08903a9df54cea4c70ee9d5291176f7b5609
Reviewed-on: https://go-review.googlesource.com/16871
Run-TryBot: Michael Matloob <matloob@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>

src/runtime/internal/atomic/textflag.h

-// Copyright 2013 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.
-
-// This file defines flags attached to various functions
-// and data objects.  The compilers, assemblers, and linker must
-// all agree on these values.
-
-// Don't profile the marked routine.  This flag is deprecated.
-#define NOPROF	1
-// It is ok for the linker to get multiple of these symbols.  It will
-// pick one of the duplicates to use.
-#define DUPOK	2
-// Don't insert stack check preamble.
-#define NOSPLIT	4
-// Put this data in a read-only section.
-#define RODATA	8
-// This data contains no pointers.
-#define NOPTR	16
-// This is a wrapper function and should not count as disabling 'recover'.
-#define WRAPPER 32
-// This function uses its incoming context register.
-#define NEEDCTXT 64
-// Allocate a word of thread local storage and store the offset from the
-// thread local base to the thread local storage in this variable.
-#define TLSBSS	256
-// Do not insert instructions to allocate a stack frame for this function.
-// Only valid on functions that declare a frame size of 0.
-// TODO(mwhudson): only implemented for ppc64x at present.
-#define NOFRAME 512