* Add a wrapper for posix <sys/uio.h>
* Add a script to generate tests for posix pxds
* Generate `tests/compile/posix_pxds.pyx`
* Update fcntl.pxd to POSIX.1-2017
* Update urls for posix/mman.pxd
* Update urls for posix/resource.pxd
* Add url for posix/select.pxd, and remove a `const`
* Update stat.pxd to POSIX.1-2017
* Update url for posix/wait.pxd

Closes https://github.com/cython/cython/issues/4522