use O(number of non zero coeffs) instead of O(number of coeffs) storage for...

use O(number of non zero coeffs) instead of O(number of coeffs) storage for the coefficient colleting/reordering


git-svn-id: file:///var/local/repositories/ffmpeg/trunk@4279 9553f0bf-9b14-0410-a0b8-cfaf0461ba5b