use 0 as maxnalsize default value.
Merge pull request #880 from ruil2/enc_quant

use 0 as maxnalsize default value.
modify dec API from void to explicit type, and some comments
Merge pull request #884 from huili2/API_dec_modify_master

modify dec API from void to explicit type
Merge remote-tracking branch 'upstream/master' into travis.osx