CMake supports the notion of installation components. Right now we have some
custom code for supporting swift components. I think that for installation
purposes, it would be nice to use the CMake component system.
This should be a non-functional change. We should still only be generating
install rules for targets and files in components we want to install, and we
still use the install ninja target to install everything.
Make a copy of Swift.xcspec that can be @VARIABLE@-substituted by cmake's configure_file mechanism, and add CMake rules to install the Xcode, vim, and emacs utils.
Swift SVN r4271
