Attempt to reland: Allow intelligibility to compile in apm (https://codereview.webrtc.org/1182323005/)

Revert of original: https://codereview.webrtc.org/1187033005/

Changes in original:
- Added files to gyp and BUILD
- Made minor fixes to get everything to compile
    and intelligibility_proc to run
- Added comments
- Auto-reformatting

New Changes:
- Added <numeric> header to intelligibility_enhancer.cc to address buildbot errors
- Switched to use WAV for i/o in intelligibility_proc.cc to address windows errors
- clean up

Note: Patch 1 duplicates Patch 7 of https://codereview.webrtc.org/1182323005/

R=andrew@webrtc.org

Review URL: https://codereview.webrtc.org/1190733004.

Cr-Commit-Position: refs/heads/master@{#9486}
diff --git a/webrtc/modules/audio_processing/audio_processing.gypi b/webrtc/modules/audio_processing/audio_processing.gypi
index 8eb2775..a4f9b39 100644
--- a/webrtc/modules/audio_processing/audio_processing.gypi
+++ b/webrtc/modules/audio_processing/audio_processing.gypi
@@ -99,6 +99,10 @@
         'high_pass_filter_impl.cc',
         'high_pass_filter_impl.h',
         'include/audio_processing.h',
+        'intelligibility/intelligibility_enhancer.cc',
+        'intelligibility/intelligibility_enhancer.h',
+        'intelligibility/intelligibility_utils.cc',
+        'intelligibility/intelligibility_utils.h',
         'level_estimator_impl.cc',
         'level_estimator_impl.h',
         'noise_suppression_impl.cc',