mac/xcode: add xcode 6.3.1 support
mac/xcode: add xcode 6.3.1 support

Closes Homebrew/homebrew#38514.

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