Fix build for configuration step in Cabal 1.18.

Prior to this commit we get the following on Cabal 1.18 on running
`cabal configure`:

    Setup.hs:91:5:
        `libraryConfig' is not a (visible) constructor field name

    Setup.hs:92:5:
        `compBuildOrder' is not a (visible) constructor field name

    Setup.hs:93:5:
        `executableConfigs' is not a (visible) constructor field name

    Setup.hs:93:57: Not in scope: `executableConfigs'

This commit removes `filterLBI` in Setup.hs that called functions
that have been removed from Cabal. This shouldn't affect the build
process on master, since the function where they are used in
Setup.hs, `filterLBI`, was added in commit #14e32add30c690b13
on Thu Mar 21 2013 and the only reference to it was removed on Sun
Jul 28 in commit #0a6bd8bd96572a9.

After this change elm compiles for me on Cabal 1.18.0 and 1.16.0.