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/system_wrappers/source/cpu_features_linux.c b/system_wrappers/source/cpu_features_linux.c
index 9c56450..004de5a 100644
--- a/system_wrappers/source/cpu_features_linux.c
+++ b/system_wrappers/source/cpu_features_linux.c
@@ -22,6 +22,7 @@
 #include <errno.h>
 #include <link.h>
 #endif
+#include "rtc_base/system/arch.h"
 #include "system_wrappers/include/cpu_features_wrapper.h"
 
 #if defined(WEBRTC_ARCH_ARM_FAMILY)