Fix build for configuration step in Cabal 1.18.

Prior to this commit the configure command fails on Cabal 1.18
with the following error:

    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. Deleting this function shouldn't affect compilation since it
seems to be unused anyway: `filterLBI`, was added in commit 14e32ad on Thu Mar
21 2013 and the only reference to it was removed on Sun Jul 28 in commit 0a6bd8 .

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