Implement the NackModule as part of the new jitter buffer.

Things done/implemented in this CL:
  - An interface that can send Nack (VCMNackSender).
  - An interface that can request KeyFrames (VCMKeyFrameRequestSender).
  - The nack module (NackModule).
  - A set of convenience functions for modular numbers (mod_ops.h).

BUG=webrtc:5514

Review URL: https://codereview.webrtc.org/1715673002

Cr-Commit-Position: refs/heads/master@{#11882}

webrtc/modules/video_coding/video_coding.gypi

@@ -36,6 +36,7 @@
         'frame_buffer.h',
         'generic_decoder.h',
         'generic_encoder.h',
+        'histogram.h',
         'inter_frame_delay.h',
         'internal_defines.h',
         'jitter_buffer.h',
@@ -44,6 +45,7 @@
         'media_opt_util.h',
         'media_optimization.h',
         'nack_fec_tables.h',
+        'nack_module.h',
         'packet.h',
         'qm_select_data.h',
         'qm_select.h',
@@ -65,10 +67,12 @@
         'generic_decoder.cc',
         'generic_encoder.cc',
         'inter_frame_delay.cc',
+        'histogram.cc',
         'jitter_buffer.cc',
         'jitter_estimator.cc',
         'media_opt_util.cc',
         'media_optimization.cc',
+        'nack_module.cc',
         'packet.cc',
         'qm_select.cc',
         'receiver.cc',