fbstring likely/unlikley ifdef for stuff that doesn't support it
fbstring likely/unlikley ifdef for stuff that doesn't support it

Summary: the fbstring specific unlikely/likely defs were missing the ifdef blocks to avoid breaking things without builtin_expect

Test Plan: fbmake runtests

Reviewed By: njormrod@fb.com

FB internal diff: D1282166

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