skylighting-extract has no version

[andreasabel]

I wanted to check which version of skylighting-extract is installed, but it seems to have very rudimentary command-line handling that does not support to print the version:

$ skylighting-extract --version
skylighting-extract: --version: openBinaryFile: does not exist (No such file or directory)

[jgm]

True, it's a very simple program. It's really just intended for use by developers; the release tarball for skylighting can be built without it, and in general users shouldn't be installing it. I don't know if it's worth building --version in, but I'd have no objections to a simple PR that does this (preferably without new build dependencies).

[jgm]

Now that I've changed the build instructions so that skylighting-extract isn't installed at all, but just run from the build directory, I don't think a version is really needed.