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}

api/rtp_headers.h

@@ -25,7 +25,6 @@
 #include "common_types.h"  // NOLINT(build/include)
 #include "rtc_base/checks.h"
 #include "rtc_base/deprecation.h"
-#include "typedefs.h"  // NOLINT(build/include)
 
 namespace webrtc {