Merge topic 'refactor-link-internals'

1ca0c0e9 cmTarget: Refactor internal imported LinkInterface map
102eea60 cmTarget: Simplify internal ComputeLinkInterfaceLibraries method
b0f57408 cmTarget: Move ComputeLinkInterfaceLibraries to internals
c69e8a55 cmTarget: Refactor internal LinkInterface map
4db3990e cmTarget: Drop 'head' argument from processSources
4b8130b8 cmTarget: Drop 'head' argument from GetSourceFiles
4c763dd1 cmTarget: Drop 'head' argument from GetLanguages
190cabe7 cmTarget: Drop 'head' argument from ComputeLinkImplementationLanguages
Merge branch 'master' into next