Initial port for hs-idris, adds several dependencies:

 - devel/hs-free
 - devel/keys
 - devel/hs-language-java
 - devel/hs-libffi
 - devel/hs-llvm-general
 - devel/hs-llvm-general-pure (formerly in lang/)
 - devel/hs-vector-binary-instances
 - math/hs-reducers
 - textproc/hs-parsers
 - textproc/hs-trifecta

idris executable was tested with both C backend and LLVM-backend.