DPH library functions don't work without -fvectorise.

[benl]

Mukesh Tiwari reports:

ghci>import Data.Array.Parallel
ghci>import Data.Array.Parallel.PArray 
ghci>let u = Data.Array.Parallel.PArray.fromList [ 1 .. 10 ]
ghci>:t u
u :: PArray Double
ghci>u
fromList<PArray> [1.0,2.0,3.0,4.0,5.0,6.0,7.0,8.0,9.0,10.0]
ghci>let v = Data.Array.Parallel.fromPArrayP u
ghci>:t v
v :: [:Double:]
ghci>lengthP v
0

[benl]

DPH programs only work when compiled with -fvectorise. Without -fvectorise, the library exports dummy, place-holder functions that don't have full implementations. We use place-holders instead of simply throwing 'error' because these functions need to have the same strictness properties as the real ones. This is mentioned at  http://www.haskell.org/haskellwiki/GHC/Data_Parallel_Haskell I'm leaving this bug open to remind us to replace the dummy place-holders with real code at some stage. There would be no point running this code for performance reasons, but at least it will be less confusing.