Move sync code to include/, switch from using platform define to a proxy header in core/

src/ports/SkBarriers_tsan.h

-/*
- * Copyright 2014 Google Inc.
- *
- * Use of this source code is governed by a BSD-style license that can be
- * found in the LICENSE file.
- */
-
-#ifndef SkBarriers_tsan_DEFINED
-#define SkBarriers_tsan_DEFINED
-
-static inline void sk_compiler_barrier() { asm volatile("" : : : "memory"); }
-
-template <typename T>
-T sk_acquire_load(T* ptr) {
-    SkASSERT(__atomic_always_lock_free(sizeof(T), ptr));
-    return __atomic_load_n(ptr, __ATOMIC_ACQUIRE);
-}
-
-template <typename T>
-T sk_consume_load(T* ptr) {
-    SkASSERT(__atomic_always_lock_free(sizeof(T), ptr));
-    return __atomic_load_n(ptr, __ATOMIC_CONSUME);
-}
-
-template <typename T>
-void sk_release_store(T* ptr, T val) {
-    SkASSERT(__atomic_always_lock_free(sizeof(T), ptr));
-    return __atomic_store_n(ptr, val, __ATOMIC_RELEASE);
-}
-
-#endif//SkBarriers_tsan_DEFINED