add missing extension pragmas
update for hashable-1.2.*
limit the number of simultaneous compiler processes

Only spawns as many compilation processes at once as there are number of CPU cores. Further kernels will be enqueued in a FIFO manner.

Avoids running out of process handles and reduces bus contention, but requires the user to link their program with the threaded RTS.
update support for scalar iteration
Merge branch 'master' of github.com:AccelerateHS/accelerate-cuda

Conflicts:
	Data/Array/Accelerate/CUDA/AST.hs
	Data/Array/Accelerate/CUDA/Array/Table.hs
	Data/Array/Accelerate/CUDA/CodeGen/Monad.hs
	Data/Array/Accelerate/CUDA/Persistent.hs