Fix how errno is set up by nn_poll().
Fix how errno is set up by nn_poll().

Signed-off-by: Martin Sustrik <4dd6061be1198639e8b05ce4fd5ead7a0dcaa0f4@250bpm.com>

zerotacg/nanomsg,nirs/nanomsg,smithed/nanomsg,simplestbest/nanomsg,pch957/nanomsg,gdamore/mamomsg,imp/nanomsg,smithed/nanomsg,ttyangf/nanomsg,modulexcite/nanomsg,tempbottle/nanomsg,pch957/nanomsg,potatogim/nanomsg,cosin2008/nanomsg.NET,kaostao/nanomsg,yan97ao/nanomsg,wfxiang08/nanomsg,nirs/nanomsg,JackDunaway/featherweight-nanomsg,simplestbest/nanomsg,tempbottle/nanomsg,simplestbest/nanomsg,zerotacg/nanomsg,linearregression/nanomsg,pakozm/nanomsg,gdamore/mamomsg,krafczyk/nanomsg,JackDunaway/featherweight-nanomsg,nirs/nanomsg,reqshark/nanomsg,gdamore/mamomsg,TTimo/nanomsg,TTimo/nanomsg,featherweight/ftw-kernel-nanomsg,modulexcite/nanomsg,hyperfact/nanomsg,imp/nanomsg,potatogim/nanomsg,wirebirdlabs/featherweight-nanomsg,ttyangf/nanomsg,linearregression/nanomsg,wirebirdlabs/featherweight-nanomsg,reqshark/nanomsg,snikulov/nanomsg,ttyangf/nanomsg,yan97ao/nanomsg,featherweight/ftw-kernel-nanomsg,cosin2008/nanomsg.NET,krafczyk/nanomsg,tempbottle/nanomsg,cosin2008/nanomsg.NET,kaostao/nanomsg,wfxiang08/nanomsg,modulexcite/nanomsg,ttyangf/nanomsg,reqshark/nanomsg,potatogim/nanomsg,thisco-de/nanomsg,yan97ao/nanomsg,hyperfact/nanomsg,TTimo/nanomsg,kaostao/nanomsg,krafczyk/nanomsg,pakozm/nanomsg,TTimo/nanomsg,smithed/nanomsg,wfxiang08/nanomsg,JackDunaway/featherweight-nanomsg,smithed/nanomsg,imp/nanomsg,thisco-de/nanomsg,zerotacg/nanomsg,wirebirdlabs/featherweight-nanomsg,kaostao/nanomsg,pch957/nanomsg,linearregression/nanomsg,snikulov/nanomsg,hyperfact/nanomsg,pakozm/nanomsg