Merge latests changes into master

This was added to the standard at some point and so there's a change in
overriding which is not easy to solve

GNAT.Expect.Poll is hanging for unknown reasons on Windows. -gnatP makes no difference. Manual polling using timeouts also doesn't read any output.

Falling back to GNAT.OS_Lib.Spawn for the moment. This means that, on Windows, there cannot be user input to the process.