nzc bug fix and clear
add according to review opinion
Merge pull request #486 from huili2/nzc_bug_fix

nzc bug fix and clear
clean redundant checks in decoder
Merge pull request #488 from licaiguo/clean-redundant-check

clean redundant checks in decoder
Merge branch 'master' of https://github.com/cisco/openh264 into add_me_test2