Fix detection of fdatasync on OSX
Fix detection of fdatasync on OSX

r3jack/beanstalkd,tdg5/beanstalkd,mickeyouyou/beanstalkd,cgvarela/beanstalkd,diditaxi/beanstalkd,potatosalad/beanstalkd,Qihoo360/beanstalkd-win,kr/beanstalkd,naderman/beanstalkd,naderman/beanstalkd,amyvmiwei/beanstalkd,PhillipMwaniki/beanstalkd,mickeyouyou/beanstalkd,handautsav/beanstalkd,Qihoo360/beanstalkd-win,wfxiang08/beanstalkd,lzpfmh/beanstalkd,orangeholic/beanstalkd,ifduyue/beanstalkd,handautsav/beanstalkd,mobliyishengyuan/beanstalkd,wfxiang08/beanstalkd,potatosalad/beanstalkd,qbdsoft/beanstalkd,wyzssw/beanstalkd,bmhatfield/beanstalkd,pinguo-xudianyang/beanstalkd,cgvarela/beanstalkd,r3jack/beanstalkd,JensRantil/beanstalkd,LomoX-Offical/beanstalkd-win,qbdsoft/beanstalkd,mobliyishengyuan/beanstalkd,justintung/beanstalkd,PhillipMwaniki/beanstalkd,lzpfmh/beanstalkd,LomoX-Offical/beanstalkd-win,bmhatfield/beanstalkd,diditaxi/beanstalkd,davies/beanstalkd,yetone/beanstalkd,orangeholic/beanstalkd,kr/beanstalkd,davies/beanstalkd,ifduyue/beanstalkd,CompendiumSoftware/beanstalkd,CompendiumSoftware/beanstalkd,amyvmiwei/beanstalkd,justintung/beanstalkd,tdg5/beanstalkd,yetone/beanstalkd,aidaima/beanstalkd,aidaima/beanstalkd,JensRantil/beanstalkd,pinguo-xudianyang/beanstalkd,wyzssw/beanstalkd,naderman/beanstalkd