supported XCode versions

[Jan Stary]

Thanks for commiting
https://github.com/janstary/macports-ports/commit/0ca6b66fd5ffd8e348812e791b25364c29052071

The file xcode_versions.ini lists the "supported" versions of xcode
for the individual MacOS versions. I wonder what exactly does it mean
for an xcode version to be there. Is there some test suite that verifies
that yes, indeed, this xcode version does work well wth this MacOS release?
Or does it simply mean it gets added there once Apple releases it?

	Jan