Fix compile on VS2015 CTP.
Fix compile on VS2015 CTP.

wieslawsoltes/Perspex,SuperJMN/Avalonia,wieslawsoltes/Perspex,AvaloniaUI/Avalonia,akrisiun/Perspex,SuperJMN/Avalonia,sagamors/Perspex,DavidKarlas/Perspex,AvaloniaUI/Avalonia,wieslawsoltes/Perspex,bbqchickenrobot/Perspex,OronDF343/Avalonia,MrDaedra/Avalonia,jkoritzinsky/Avalonia,OronDF343/Avalonia,kekekeks/Perspex,jkoritzinsky/Avalonia,jazzay/Perspex,kekekeks/Perspex,AvaloniaUI/Avalonia,wieslawsoltes/Perspex,jkoritzinsky/Perspex,grokys/Perspex,SuperJMN/Avalonia,punker76/Perspex,wieslawsoltes/Perspex,SuperJMN/Avalonia,wieslawsoltes/Perspex,jkoritzinsky/Avalonia,Perspex/Perspex,grokys/Perspex,AvaloniaUI/Avalonia,susloparovdenis/Avalonia,MrDaedra/Avalonia,AvaloniaUI/Avalonia,SuperJMN/Avalonia,danwalmsley/Perspex,SuperJMN/Avalonia,susloparovdenis/Perspex,ncarrillo/Perspex,jkoritzinsky/Avalonia,jkoritzinsky/Avalonia,susloparovdenis/Perspex,Perspex/Perspex,wieslawsoltes/Perspex,jkoritzinsky/Avalonia,SuperJMN/Avalonia,tshcherban/Perspex,susloparovdenis/Avalonia,AvaloniaUI/Avalonia,AvaloniaUI/Avalonia,jkoritzinsky/Avalonia