Add missing s6_addr16 define for MacOSX targets
Add missing s6_addr16 define for MacOSX targets

Summary:
This is a known issue on Darwin

@override-unit-failures

Test Plan: folly/detail/IPAddress.h compiles on a mac

Reviewed By: joelm@fb.com

FB internal diff: D1499795

kernelim/folly,loverszhaokai/folly,raphaelamorim/folly,PoisonBOx/folly,upsoft/folly,charsyam/folly,SammyK/folly,Eagle-X/folly,hongliangzhao/folly,nickhen/folly,yangjin-unique/folly,reddit/folly,xzmagic/folly,sakishum/folly,PPC64/folly,sonnyhu/folly,wildinto/folly,mqeizi/folly,nickhen/folly,Hincoin/folly,chjp2046/folly,arg0/folly,chjp2046/folly,guker/folly,upsoft/folly,yangjin-unique/folly,alexst07/folly,tempbottle/folly,shaobz/folly,theiver9827/folly,fw1121/folly,kernelim/folly,facebook/folly,stonegithubs/folly,raphaelamorim/folly,colemancda/folly,bobegir/folly,upsoft/folly,leolujuyi/folly,theiver9827/folly,kernelim/folly,chjp2046/folly,brunomorishita/folly,SeanRBurton/folly,project-zerus/folly,renyinew/folly,colemancda/folly,fw1121/folly,theiver9827/folly,doctaweeks/folly,bikong2/folly,shaobz/folly,guker/folly,mqeizi/folly,lifei/folly,project-zerus/folly,lifei/folly,xzmagic/folly,mqeizi/folly,arg0/folly,bikong2/folly,wildinto/folly,bsampath/folly,tomhughes/folly,cppfool/folly,CJstar/folly,tempbottle/folly,raphaelamorim/folly,gaoyingie/folly,wildinto/folly,fw1121/folly,Orvid/folly,romange/folly,rklabs/folly,rklabs/folly,loverszhaokai/folly,CJstar/folly,hongliangzhao/folly,bikong2/folly,reddit/folly,floxard/folly,Eagle-X/folly,arg0/folly,PPC64/folly,chjp2046/folly,colemancda/folly,arg0/folly,romange/folly,guker/folly,lifei/folly,tomhughes/folly,constantine001/folly,juniway/folly,yangjin-unique/folly,clearlinux/folly,cppfool/folly,bikong2/folly,constantine001/folly,bobegir/folly,KSreeHarsha/folly,cole14/folly,cole14/folly,shaobz/folly,xzmagic/folly,colemancda/folly,mqeizi/folly,PPC64/folly,fw1121/folly,gavioto/folly,renyinew/folly,charsyam/folly,tempbottle/folly,Orvid/folly,gavioto/folly,chjp2046/folly,loverszhaokai/folly,romange/folly,floxard/folly,SammyK/folly,fw1121/folly,brunomorishita/folly,zhiweicai/folly,Eagle-X/folly,juniway/folly,SammyK/folly,tomhughes/folly,arg0/folly,brunomorishita/folly,KSreeHarsha/folly,kernelim/folly,floxard/folly,rklabs/folly,yangjin-unique/folly,stonegithubs/folly,Eagle-X/folly,bobegir/folly,leolujuyi/folly,leolujuyi/folly,cppfool/folly,ykarlsbrun/folly,PoisonBOx/folly,clearlylin/folly,CJstar/folly,lifei/folly,ykarlsbrun/folly,mqeizi/folly,alexst07/folly,tomhughes/folly,Orvid/folly,tomhughes/folly,project-zerus/folly,bobegir/folly,juniway/folly,loverszhaokai/folly,renyinew/folly,renyinew/folly,sakishum/folly,gaoyingie/folly,SammyK/folly,cole14/folly,bowlofstew/folly,gavioto/folly,Eagle-X/folly,doctaweeks/folly,bowlofstew/folly,constantine001/folly,loverszhaokai/folly,alexst07/folly,reddit/folly,stonegithubs/folly,bowlofstew/folly,project-zerus/folly,doctaweeks/folly,nickhen/folly,romange/folly,gavioto/folly,bowlofstew/folly,project-zerus/folly,ykarlsbrun/folly,rklabs/folly,reddit/folly,alexst07/folly,clearlinux/folly,bsampath/folly,clearlylin/folly,doctaweeks/folly,Hincoin/folly,renyinew/folly,raphaelamorim/folly,theiver9827/folly,shaobz/folly,brunomorishita/folly,tempbottle/folly,kernelim/folly,loversInJapan/folly,clearlylin/folly,colemancda/folly,cppfool/folly,gavioto/folly,Orvid/folly,KSreeHarsha/folly,SammyK/folly,romange/folly,stonegithubs/folly,leolujuyi/folly,ykarlsbrun/folly,facebook/folly,constantine001/folly,shaobz/folly,stonegithubs/folly,KSreeHarsha/folly,loversInJapan/folly,lifei/folly,sonnyhu/folly,facebook/folly,PoisonBOx/folly,PPC64/folly,leolujuyi/folly,upsoft/folly,Orvid/folly,PoisonBOx/folly,clearlylin/folly,bobegir/folly,SeanRBurton/folly,cole14/folly,doctaweeks/folly,gaoyingie/folly,juniway/folly,zhiweicai/folly,sakishum/folly,bowlofstew/folly,gaoyingie/folly,hongliangzhao/folly,guker/folly,clearlinux/folly,wildinto/folly,constantine001/folly,clearlinux/folly,Hincoin/folly,SeanRBurton/folly,sonnyhu/folly,Hincoin/folly,floxard/folly,SeanRBurton/folly,sonnyhu/folly,ykarlsbrun/folly,guker/folly,yangjin-unique/folly,nickhen/folly,CJstar/folly,floxard/folly,zhiweicai/folly,KSreeHarsha/folly,sonnyhu/folly,rklabs/folly,xzmagic/folly,tempbottle/folly,cppfool/folly,reddit/folly,hongliangzhao/folly,clearlinux/folly,zhiweicai/folly,alexst07/folly,PoisonBOx/folly,theiver9827/folly,clearlylin/folly,charsyam/folly,gaoyingie/folly,bsampath/folly,SeanRBurton/folly,cole14/folly,juniway/folly,bsampath/folly,charsyam/folly,xzmagic/folly,CJstar/folly,upsoft/folly,brunomorishita/folly,hongliangzhao/folly,bsampath/folly,raphaelamorim/folly,loversInJapan/folly,facebook/folly,PPC64/folly,sakishum/folly,sakishum/folly,Hincoin/folly,wildinto/folly,nickhen/folly,loversInJapan/folly,loversInJapan/folly,facebook/folly,zhiweicai/folly,bikong2/folly