external: import cpu_features library

Taken from https://github.com/google/cpu_features at revision
26133d3b620c2c27f31d571efd27371100f891e9

external/cpu_features/include/cpuinfo_aarch64.h

@@ -0,0 +1,65 @@
+// Copyright 2017 Google Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//    http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef CPU_FEATURES_INCLUDE_CPUINFO_AARCH64_H_
+#define CPU_FEATURES_INCLUDE_CPUINFO_AARCH64_H_
+
+#include "cpu_features_macros.h"
+
+CPU_FEATURES_START_CPP_NAMESPACE
+
+typedef struct {
+  int fp : 1;     // Floating-point.
+  int asimd : 1;  // Advanced SIMD.
+  int aes : 1;    // Hardware-accelerated Advanced Encryption Standard.
+  int pmull : 1;  // Polynomial multiply long.
+  int sha1 : 1;   // Hardware-accelerated SHA1.
+  int sha2 : 1;   // Hardware-accelerated SHA2-256.
+  int crc32 : 1;  // Hardware-accelerated CRC-32.
+
+  // Make sure to update Aarch64FeaturesEnum below if you add a field here.
+} Aarch64Features;
+
+typedef struct {
+  Aarch64Features features;
+  int implementer;
+  int variant;
+  int part;
+  int revision;
+} Aarch64Info;
+
+Aarch64Info GetAarch64Info(void);
+
+////////////////////////////////////////////////////////////////////////////////
+// Introspection functions
+
+typedef enum {
+  AARCH64_FP,
+  AARCH64_ASIMD,
+  AARCH64_AES,
+  AARCH64_PMULL,
+  AARCH64_SHA1,
+  AARCH64_SHA2,
+  AARCH64_CRC32,
+  AARCH64_LAST_,
+} Aarch64FeaturesEnum;
+
+int GetAarch64FeaturesEnumValue(const Aarch64Features* features,
+                                Aarch64FeaturesEnum value);
+
+const char* GetAarch64FeaturesEnumName(Aarch64FeaturesEnum);
+
+CPU_FEATURES_END_CPP_NAMESPACE
+
+#endif  // CPU_FEATURES_INCLUDE_CPUINFO_AARCH64_H_