Support os.PathLike for filename inputs
This more or less just comes down to calling PyOS_FSPath
on filename input types.
pycairo does this already for example: https://github.com/pygobject/pycairo/blob/06bc4816c32f2ff5e6376b5de9020923e7500977/cairo/misc.c#L57
after this !195 (merged) could be reverted
Edited by Christoph Reiter