Add 'void' type in dtype_to_ctype mapping

Use type qualifier __restrict__ instead of keyword restrict

because C++ does not have the latter.

FWIW, CUDA already used __restrict__ before this commit!
I guess that means, `CudaRestrictPointer` could be deprecated?

See merge request !1

because C++ does not have the latter.

FWIW, CUDA already used __restrict__ before this commit!
I guess that means, `CudaRestrictPointer` could be deprecated?

[bugfix] Add handler for CustomLoop

I guess this has been forgotten in the first place.

Block constructor should be able to silently accept another Block object

Block constructor should be able to silently accept another Block object and initialise itself to its contents. For ease of use

Two new classes added for InlineInitializers and IfDefs