PointerType should be rendered differently in OpenCL backend

OpenCL macOS support

See merge request !87

Staggered field access and staggered fields with fluxes to edges/faces

See merge request !86

Fix create_cuda_kernel to allow CUSTOM_FIELDS to have a different size

See merge request !83

Remove duplicated uint typedef

See merge request !84

Add Field.itemsize (yields Field.dtype.numpy_dtype.itemsize)

See merge request !82

Oops, forgot a return in TextureCachedField.reproducible_hash

See merge request !81

TextureCachedField was using `hash(...)` to disambiguate its instances.
However, `hash` is randomized and will hinder reproducible code
generation

Use reproducible hashlib for representing TextureCachedField

See merge request pycodegen/pystencils!80

Add sympy to known_third_party in .isort.cfg

See merge request pycodegen/pystencils!79

I have installed the newest master of SymPy as editable package.
So `isort` thinks it's one of our libraries.
With this config SymPy is declared as a third party dependency.

Support complex numbers

See merge request pycodegen/pystencils!72

Bugfix: textures should be implemented as textures without changes

See merge request pycodegen/pystencils!73

Add __str__ representation for TextureDeclaration

See merge request pycodegen/pystencils!74

Add option to omit globals when printing C code

See merge request pycodegen/pystencils!75

Run opencl without pycuda

Closes #15

See merge request pycodegen/pystencils!77

correctly print RNG nodes

See merge request pycodegen/pystencils!78