doctor: update xcode chceck
doctor: update xcode chceck

* 4.3.3 is the latest on 10.7
* Give up if we don't know what the latest is (10.8 and beyond)

amar-laksh/brew_sudo,maxim-belkin/brew,mistydemeo/homebrew,maxim-belkin/brew,mistydemeo/homebrew,staticfloat/brew,MikeMcQuaid/brew,zmwangx/brew,zmwangx/brew,toonetown/homebrew,reitermarkus/brew,jmsundar/brew,muellermartin/dist,reitermarkus/brew,mahori/brew,alyssais/brew,MikeMcQuaid/brew,reelsense/brew,amar-laksh/brew_sudo,staticfloat/brew,alyssais/brew,Linuxbrew/brew,Homebrew/brew,aw1621107/brew,hanxue/linuxbrew,aw1621107/brew,maxim-belkin/brew,reelsense/brew,Linuxbrew/brew,reitermarkus/brew,Homebrew/brew,EricFromCanada/brew,aw1621107/brew,hanxue/linuxbrew,konqui/brew,tonyg/homebrew,EricFromCanada/brew,vitorgalvao/brew,DomT4/brew,mgrimes/brew,Linuxbrew/brew,Homebrew/brew,pseudocody/brew,mahori/brew,amar-laksh/brew_sudo,mahori/brew,ilovezfs/brew,DomT4/brew,EricFromCanada/brew,MikeMcQuaid/brew,gordonmcshane/homebrew,Homebrew/brew,rwhogg/brew,claui/brew,claui/brew,jmsundar/brew,gordonmcshane/homebrew,sjackman/homebrew,toonetown/homebrew,JCount/brew,JCount/brew,mahori/brew,tonyg/homebrew,mistydemeo/homebrew,ilovezfs/brew,AnastasiaSulyagina/brew,JCount/brew,alyssais/brew,rwhogg/brew,reelsense/brew,AnastasiaSulyagina/brew,sjackman/homebrew,claui/brew,zmwangx/brew,vitorgalvao/brew,EricFromCanada/brew,staticfloat/brew,nandub/brew,nandub/brew,gregory-nisbet/brew,muellermartin/dist,vitorgalvao/brew,pseudocody/brew,gregory-nisbet/brew,konqui/brew,bfontaine/brew,claui/brew,mgrimes/brew,DomT4/brew,mgrimes/brew,gordonmcshane/homebrew,konqui/brew,muellermartin/dist,Linuxbrew/brew,rwhogg/brew,nandub/brew,vitorgalvao/brew,sjackman/homebrew,bfontaine/brew,bfontaine/brew,jmsundar/brew,konqui/brew,JCount/brew,tonyg/homebrew,sjackman/homebrew,AnastasiaSulyagina/brew,pseudocody/brew,MikeMcQuaid/brew,palxex/brew,DomT4/brew,hanxue/linuxbrew,reitermarkus/brew,palxex/brew,palxex/brew,nandub/brew,gregory-nisbet/brew,toonetown/homebrew,ilovezfs/brew