Move the aec_rdft* files to a more proper place beneath APM and make them thread-safe.

webrtc/modules/audio_processing/utility/ooura_fft.h

Index: webrtc/modules/audio_processing/utility/ooura_fft.h
diff --git a/webrtc/modules/audio_processing/utility/ooura_fft.h b/webrtc/modules/audio_processing/utility/ooura_fft.h
new file mode 100644
index 0000000000000000000000000000000000000000..a1b9f04f5442be10aa3edc4657c2056ed454bbfe
--- /dev/null
+++ b/webrtc/modules/audio_processing/utility/ooura_fft.h
@@ -0,0 +1,60 @@
+/*
+ *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef WEBRTC_MODULES_AUDIO_PROCESSING_UTILITY_OOURA_FFT_H_
+#define WEBRTC_MODULES_AUDIO_PROCESSING_UTILITY_OOURA_FFT_H_
+
+#include "webrtc/typedefs.h"
+
+namespace webrtc {
+
+#if defined(WEBRTC_ARCH_X86_FAMILY)
+void cft1st_128_SSE2(float* a);
+void cftmdl_128_SSE2(float* a);
+void rftfsub_128_SSE2(float* a);
+void rftbsub_128_SSE2(float* a);
+#endif
+
+#if defined(MIPS_FPU_LE)
+void cft1st_128_mips(float* a);
+void cftmdl_128_mips(float* a);
+void rftfsub_128_mips(float* a);
+void rftbsub_128_mips(float* a);
+#endif
+
+#if defined(WEBRTC_HAS_NEON)
+void cft1st_128_neon(float* a);
+void cftmdl_128_neon(float* a);
+void rftfsub_128_neon(float* a);
+void rftbsub_128_neon(float* a);
+#endif
+
+class OouraFft {
+ public:
+  OouraFft();
+  ~OouraFft();
+  void Fft(float* a) const;
+  void InverseFft(float* a) const;
+
+ private:
+  void cft1st_128(float* a) const;
+  void cftmdl_128(float* a) const;
+  void rftfsub_128(float* a) const;
+  void rftbsub_128(float* a) const;
+
+  void cftfsub_128(float* a) const;
+  void cftbsub_128(float* a) const;
+  void bitrv2_128(float* a) const;
+  bool use_sse2_;
+};
+
+}  // namespace webrtc
+
+#endif  // WEBRTC_MODULES_AUDIO_PROCESSING_UTILITY_OOURA_FFT_H_