Add missing stdio.h header in files using scanf/sscanf function.

Various files in webrtc codebase use scanf/sscanf function without
including stdio.h header file which is supposed to define it. This
somehow works when using glibc, but fails with uClibc.

Bug: webrtc:8641
Change-Id: Ie4ae17af32b32ed8cea567166b6b0e5193966995
Reviewed-on: https://webrtc-review.googlesource.com/32261
Commit-Queue: Stefan Holmer <stefan@webrtc.org>
Reviewed-by: Erik Språng <sprang@webrtc.org>
Reviewed-by: Stefan Holmer <stefan@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#21775}
diff --git a/AUTHORS b/AUTHORS
index 6fe7748..00b6b44 100644
--- a/AUTHORS
+++ b/AUTHORS
@@ -81,3 +81,4 @@
 Vonage Holdings Corp. <*@vonage.com>
 Wire Swiss GmbH <*@wire.com>
 Miguel Paris <mparisdiaz@gmail.com>
+Vewd Software AS <*@vewd.com>