various minor fixes and refactorings

src/pystencils/backend/arrays.py

src/pystencils/backend/ast/analysis.py

src/pystencils/backend/emission.py

src/pystencils/backend/kernelcreation/context.py

src/pystencils/backend/platforms/generic_cpu.py

src/pystencils/backend/platforms/platform.py

src/pystencils/backend/platforms/x86.py

...encils/backend/transformations/erase_anonymous_structs.py

src/pystencils/kernelcreation.py