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}
diff --git a/rtc_base/task_queue_libevent.cc b/rtc_base/task_queue_libevent.cc
index b6e6353..d3b1a7c 100644
--- a/rtc_base/task_queue_libevent.cc
+++ b/rtc_base/task_queue_libevent.cc
@@ -24,6 +24,7 @@
 #include "rtc_base/platform_thread.h"
 #include "rtc_base/refcount.h"
 #include "rtc_base/refcountedobject.h"
+#include "rtc_base/system/unused.h"
 #include "rtc_base/task_queue.h"
 #include "rtc_base/task_queue_posix.h"
 #include "rtc_base/timeutils.h"