Move RTP module activation into PayloadRouter.

Simplifies PayloadRouter to not accept dynamically-changing modules as
well as usage of PayloadRouter inside ViEChannel::SetSendCodec.

BUG=webrtc:5494
R=stefan@webrtc.org
TBR=mflodman@webrtc.org

Review URL: https://codereview.webrtc.org/1725363003 .

Cr-Commit-Position: refs/heads/master@{#11787}
diff --git a/webrtc/common_types.h b/webrtc/common_types.h
index 2999bc9..16174dc 100644
--- a/webrtc/common_types.h
+++ b/webrtc/common_types.h
@@ -37,7 +37,7 @@
 #define NULL 0
 #endif
 
-#define RTP_PAYLOAD_NAME_SIZE 32
+#define RTP_PAYLOAD_NAME_SIZE 32u
 
 #if defined(WEBRTC_WIN) || defined(WIN32)
 // Compares two strings without regard to case.