Does everyone support __has_include() now?

Let's find out.

Change-Id: I8ff2103c389d6627f3963a2f067baa0a211647c9
Reviewed-on: https://skia-review.googlesource.com/134510
Commit-Queue: Ben Wagner <bungeman@google.com>
Auto-Submit: Mike Klein <mtklein@chromium.org>
Reviewed-by: Ben Wagner <bungeman@google.com>

src/codec/SkHeifCodec.h

@@ -16,10 +16,6 @@
 #include "SkSwizzler.h"
 #include "SkStream.h"
 
-#if !defined(__has_include)
-    #define __has_include(x) 0
-#endif
-
 #if __has_include("HeifDecoderAPI.h")
     #include "HeifDecoderAPI.h"
 #else

src/core/SkCpu.cpp

@@ -8,10 +8,6 @@
 #include "SkCpu.h"
 #include "SkOnce.h"
 
-#if !defined(__has_include)
-    #define __has_include(x) 0
-#endif
-
 #if defined(SK_CPU_X86)
     #if defined(SK_BUILD_FOR_WIN)
         #include <intrin.h>