Removes the legacy spellings of the thread annotation macros/functions

by default.

The compatibility macro `ABSL_LEGACY_THREAD_ANNOTATIONS` can be
defined on the compile command-line to temporarily restore these
spellings. All of the thread annotation macros are available under
ABSL_ prefixed spellings in `absl/base/thread_annotations.h`. The
compatibility macro and the legacy spellings will be removed in the
future.

See google/fuzztest#41

PiperOrigin-RevId: 478498273
Change-Id: I120ad6480d031642bf95a11bf72ab883d9161810

absl/base/internal/thread_annotations.h

@@ -38,6 +38,13 @@
 #ifndef ABSL_BASE_INTERNAL_THREAD_ANNOTATIONS_H_
 #define ABSL_BASE_INTERNAL_THREAD_ANNOTATIONS_H_
 
+// ABSL_LEGACY_THREAD_ANNOTATIONS is a *temporary* compatibility macro that can
+// be defined on the compile command-line to restore the legacy spellings of the
+// thread annotations macros/functions. The macros in this file are available
+// under ABSL_ prefixed spellings in absl/base/thread_annotations.h. This macro
+// and the legacy spellings will be removed in the future.
+#ifdef ABSL_LEGACY_THREAD_ANNOTATIONS
+
 #if defined(__clang__)
 #define THREAD_ANNOTATION_ATTRIBUTE__(x)   __attribute__((x))
 #else
@@ -268,4 +275,6 @@ inline T& ts_unchecked_read(T& v) NO_THREAD_SAFETY_ANALYSIS {
 
 }  // namespace thread_safety_analysis
 
+#endif  // defined(ABSL_LEGACY_THREAD_ANNOTATIONS)
+
 #endif  // ABSL_BASE_INTERNAL_THREAD_ANNOTATIONS_H_