fixed a compiler warning and cleaned up various other  atomic ops idioms which need their results checked.
fixed a compiler warning and cleaned up various other 
atomic ops idioms which need their results checked.


TEST= ./scons sel_universal platform=x86-64 sdl_sel_universal=1
Review URL: http://codereview.chromium.org/7657016

git-svn-id: 721b910a23eff8a86f00c8fd261a7587cddf18f8@6557 fcba33aa-ac0c-11dd-b9e7-8d5594d729c2

sbc100/native_client,sbc100/native_client,sbc100/native_client,sbc100/native_client,nacl-webkit/native_client,nacl-webkit/native_client,nacl-webkit/native_client,nacl-webkit/native_client,sbc100/native_client,nacl-webkit/native_client,sbc100/native_client