Changes to filepath(3)

Changes to filepath:
commit 8dd8a3616f137cb78af3366464bcf9cecf81ff75
Author: Herbert Valerio Riedel <hvr@gnu.org>
Date:   Fri Oct 18 11:33:43 2013 +0200

    Add .travis.yml to test compilation with older GHCs

    This is currently a proof of concept and might be disabled again.

    Signed-off-by: Herbert Valerio Riedel <hvr@gnu.org>

commit 0e2e7997d41e71300b90c72470d0143f59fb9b8f
Author: Herbert Valerio Riedel <hvr@gnu.org>
Date:   Fri Oct 18 11:26:33 2013 +0200

    Refactor & update `filepath.cabal` to `cabal-version>=1.10`

    As of this commit, `filepath` compiles cleanly with
    GHC 6.10/6.12/7.0/7.2/7.4/7.6/HEAD.

    Signed-off-by: Herbert Valerio Riedel <hvr@gnu.org>

commit 35c19074f3a22eba5f5322bc35ef3ced24032ef3
Author: Herbert Valerio Riedel <hvr@gnu.org>
Date:   Fri Oct 18 11:18:10 2013 +0200

    Clean up CPP/Haddock interaction

    This removes the obsolete pre-Haddock2 `__HADDOCK__` conditional check
    which isn't supported anymore by Haddock2 (and in fact the conditional
    isn't needed anyway).

    This commit also moves more content into the
    `System/FilePath/Internal.hs` template that's `#include`d by
    `System/FilePath/{Posix,Windows}.hs` and as a side-effect, a part of the
    Haddock module-level documentation containing usage examples is now
    shown again in the generated HTML output.

    Signed-off-by: Herbert Valerio Riedel <hvr@gnu.org>