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. This shouldn't affect the build
process on master, since the function where they are used in
Setup.hs, `filterLBI`, was added in commit
14e32add30c690b1309252d530afbea29cc448ec on Thu Mar 21 2013 and the
only reference to it was removed on Sun Jul 28 in commit
0a6bd8bd96572a9a9b81df717bf9cdb002897663.

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