[Cleanup] Add missing #include. Remove useless ones.

This CL is the result of running include-what-you-use tool on part
of the code base (audio target and dependencies) plus manual fixes.

bug: webrtc:8311
Change-Id: I277d281ce943c3ecc1bd45fd8d83055931743604
Reviewed-on: https://webrtc-review.googlesource.com/c/106280
Commit-Queue: Yves Gerey <yvesg@google.com>
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Reviewed-by: Patrik Höglund <phoglund@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#25311}
diff --git a/rtc_base/platform_thread.cc b/rtc_base/platform_thread.cc
index 79d9d53..ba84b6a 100644
--- a/rtc_base/platform_thread.cc
+++ b/rtc_base/platform_thread.cc
@@ -10,15 +10,17 @@
 
 #include "rtc_base/platform_thread.h"
 
+#if !defined(WEBRTC_WIN)
+#include <sched.h>
+#endif
+#include <stdint.h>
+#include <time.h>
+#include <algorithm>
+
 #include "rtc_base/atomicops.h"
 #include "rtc_base/checks.h"
 #include "rtc_base/timeutils.h"
 
-#if defined(WEBRTC_LINUX)
-#include <sys/prctl.h>
-#include <sys/syscall.h>
-#endif
-
 namespace rtc {
 namespace {
 #if defined(WEBRTC_WIN)