Moved sequence number specific operations from mod_ops.h
to sequence_number_util.h

Also in this CL:
  - Implemented a MinDiff function which finds the smallest diff of two
    wrapping numbers.
  - Implemented comparators for sequence numbers.

BUG=
R=mflodman@webrtc.org, tommi@webrtc.org, torbjorng@webrtc.org

Review URL: https://codereview.webrtc.org/1814753002 .

Cr-Commit-Position: refs/heads/master@{#12083}
diff --git a/webrtc/modules/video_coding/histogram.cc b/webrtc/modules/video_coding/histogram.cc
index e07d50b..f2aa6ea 100644
--- a/webrtc/modules/video_coding/histogram.cc
+++ b/webrtc/modules/video_coding/histogram.cc
@@ -12,7 +12,7 @@
 
 #include <algorithm>
 
-#include "webrtc/base/mod_ops.h"
+#include "webrtc/modules/video_coding/sequence_number_util.h"
 
 namespace webrtc {
 namespace video_coding {