Remove the different block lengths in ns_core

Relanding the CL: https://webrtc-codereview.appspot.com/30539004/
It had to be reverted because some development code was uploaded by mistake.

TBR=bjornv@webrtc.org

BUG=webrtc:3811

Review URL: https://webrtc-codereview.appspot.com/28589005

git-svn-id: http://webrtc.googlecode.com/svn/trunk@7307 4adac7df-926f-26a2-2b94-8c16560cd09d