Disable VDSO on MSVC
Disable VDSO on MSVC

Summary: MSVC will never be able to load VDSO, and doesn't even have dlopen, so just return `nullptr`, and let the fallback mechanisms handle it from there.
Closes #282

Reviewed By: @yfeldblum

Differential Revision: D2307461

Pulled By: @sgolemon

bowlofstew/folly,lifei/folly,arg0/folly,KSreeHarsha/folly,bowlofstew/folly,fw1121/folly,brunomorishita/folly,sakishum/folly,Eagle-X/folly,gaoyingie/folly,fw1121/folly,gaoyingie/folly,sakishum/folly,stonegithubs/folly,Orvid/folly,constantine001/folly,mqeizi/folly,constantine001/folly,tomhughes/folly,reddit/folly,floxard/folly,upsoft/folly,SeanRBurton/folly,tempbottle/folly,guker/folly,clearlylin/folly,hongliangzhao/folly,juniway/folly,bikong2/folly,theiver9827/folly,tomhughes/folly,raphaelamorim/folly,yangjin-unique/folly,bobegir/folly,juniway/folly,yangjin-unique/folly,raphaelamorim/folly,loversInJapan/folly,Orvid/folly,rklabs/folly,hongliangzhao/folly,guker/folly,KSreeHarsha/folly,hongliangzhao/folly,leolujuyi/folly,KSreeHarsha/folly,juniway/folly,Hincoin/folly,mqeizi/folly,tempbottle/folly,juniway/folly,upsoft/folly,upsoft/folly,zhiweicai/folly,Hincoin/folly,CJstar/folly,gavioto/folly,PoisonBOx/folly,theiver9827/folly,tempbottle/folly,brunomorishita/folly,facebook/folly,sakishum/folly,alexst07/folly,gaoyingie/folly,floxard/folly,stonegithubs/folly,mqeizi/folly,charsyam/folly,SammyK/folly,SeanRBurton/folly,Eagle-X/folly,SeanRBurton/folly,CJstar/folly,leolujuyi/folly,mqeizi/folly,guker/folly,gavioto/folly,fw1121/folly,arg0/folly,rklabs/folly,sonnyhu/folly,brunomorishita/folly,loversInJapan/folly,renyinew/folly,Eagle-X/folly,zhiweicai/folly,gavioto/folly,bobegir/folly,PoisonBOx/folly,SammyK/folly,loversInJapan/folly,hongliangzhao/folly,PoisonBOx/folly,zhiweicai/folly,arg0/folly,bobegir/folly,upsoft/folly,zhiweicai/folly,rklabs/folly,stonegithubs/folly,raphaelamorim/folly,theiver9827/folly,Eagle-X/folly,alexst07/folly,fw1121/folly,tomhughes/folly,PPC64/folly,Orvid/folly,KSreeHarsha/folly,bikong2/folly,loversInJapan/folly,theiver9827/folly,facebook/folly,reddit/folly,clearlylin/folly,floxard/folly,lifei/folly,gaoyingie/folly,leolujuyi/folly,raphaelamorim/folly,mqeizi/folly,SammyK/folly,leolujuyi/folly,SeanRBurton/folly,bikong2/folly,charsyam/folly,bowlofstew/folly,bobegir/folly,tomhughes/folly,charsyam/folly,sonnyhu/folly,zhiweicai/folly,facebook/folly,constantine001/folly,leolujuyi/folly,tempbottle/folly,PoisonBOx/folly,sonnyhu/folly,arg0/folly,juniway/folly,brunomorishita/folly,renyinew/folly,bowlofstew/folly,gaoyingie/folly,alexst07/folly,SammyK/folly,tempbottle/folly,gavioto/folly,Orvid/folly,charsyam/folly,rklabs/folly,Hincoin/folly,renyinew/folly,CJstar/folly,PPC64/folly,guker/folly,alexst07/folly,yangjin-unique/folly,yangjin-unique/folly,Orvid/folly,rklabs/folly,sonnyhu/folly,CJstar/folly,facebook/folly,renyinew/folly,PPC64/folly,clearlylin/folly,PPC64/folly,renyinew/folly,theiver9827/folly,SeanRBurton/folly,hongliangzhao/folly,lifei/folly,bowlofstew/folly,KSreeHarsha/folly,PoisonBOx/folly,Eagle-X/folly,sakishum/folly,raphaelamorim/folly,gavioto/folly,bobegir/folly,floxard/folly,facebook/folly,arg0/folly,lifei/folly,fw1121/folly,reddit/folly,sakishum/folly,yangjin-unique/folly,CJstar/folly,PPC64/folly,tomhughes/folly,reddit/folly,SammyK/folly,alexst07/folly,clearlylin/folly,clearlylin/folly,stonegithubs/folly,guker/folly,reddit/folly,constantine001/folly,Hincoin/folly,Hincoin/folly,stonegithubs/folly,constantine001/folly,sonnyhu/folly,floxard/folly,bikong2/folly,loversInJapan/folly,brunomorishita/folly,lifei/folly,bikong2/folly,upsoft/folly