audio_processing/agc: Solved building with AGC_DEBUG + few style changes

webrtc did not build if AGC_DEBUG was turned on. This CL fixes that. Has no impact on performance since it is development/debug code.

* Name change to WEBRT_AGC_DEBUG_DUMP
* Added build flag agc_debug_dump to .gypi
* Added missing "%d" in printf at two places
* Some line length related style changes

Tested audioproc and modules_unittests with GYP_DEFINES=agc_debug_dump=1 webrtc/build/gyp_webrtc

BUG=N/A
TESTED=locally and trybots
R=aluebs@webrtc.org, kwiberg@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/31429004

git-svn-id: http://webrtc.googlecode.com/svn/trunk@7271 4adac7df-926f-26a2-2b94-8c16560cd09d