Delete root header file typedef.h.

Usage replaced with stdint.h, rtc_base/system/arch.h and
rtc_base/system/unused.h, as appropriate.

Bug: webrtc:6854
Change-Id: I97225465d14b969903d92979e2df3c3c05d35f18
Reviewed-on: https://webrtc-review.googlesource.com/90249
Reviewed-by: Niklas Enbom <niklas.enbom@webrtc.org>
Reviewed-by: Fredrik Solenberg <solenberg@webrtc.org>
Commit-Queue: Niels Moller <nisse@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#24100}

modules/audio_coding/codecs/pcm16b/pcm16b.c

@@ -10,8 +10,6 @@
 
 #include "modules/audio_coding/codecs/pcm16b/pcm16b.h"
 
-#include "typedefs.h"  // NOLINT(build/include)
-
 size_t WebRtcPcm16b_Encode(const int16_t* speech,
                            size_t len,
                            uint8_t* encoded) {

modules/audio_coding/codecs/pcm16b/pcm16b.h

@@ -15,8 +15,7 @@
  */
 
 #include <stddef.h>
-
-#include "typedefs.h"  // NOLINT(build/include)
+#include <stdint.h>
 
 #ifdef __cplusplus
 extern "C" {