Revert 66a4ea1c80fa36fe348b3d5ad6d2f6c61cf21c05
Revert 66a4ea1c80fa36fe348b3d5ad6d2f6c61cf21c05

Refusing to unlink files from another keg introduced issues when
files changed between formula versions; for instance, this
introduced issues when upgrading from gtk+ 2.24.10 to 2.24.11.

See Homebrew/homebrew#12778.

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