Fixing WebRTC after moving from src/webrtc to src/

In https://webrtc-review.googlesource.com/c/src/+/1560 we moved WebRTC
from src/webrtc to src/ (in order to preserve an healthy git history).
This CL takes care of fixing header guards, #include paths, etc...

NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
TBR=tommi@webrtc.org


Bug: chromium:611808
Change-Id: Iea91618212bee0af16aa3f05071eab8f93706578
Reviewed-on: https://webrtc-review.googlesource.com/1561
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Reviewed-by: Henrik Kjellander <kjellander@webrtc.org>
Commit-Queue: Mirko Bonadei <mbonadei@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#19846}
diff --git a/sdk/objc/Framework/Classes/PeerConnection/RTCRtpFragmentationHeader.mm b/sdk/objc/Framework/Classes/PeerConnection/RTCRtpFragmentationHeader.mm
index 541fd45..87c88a4 100644
--- a/sdk/objc/Framework/Classes/PeerConnection/RTCRtpFragmentationHeader.mm
+++ b/sdk/objc/Framework/Classes/PeerConnection/RTCRtpFragmentationHeader.mm
@@ -10,7 +10,7 @@
 
 #import "WebRTC/RTCVideoCodec.h"
 
-#include "webrtc/modules/include/module_common_types.h"
+#include "modules/include/module_common_types.h"
 
 @implementation RTCRtpFragmentationHeader