Error-proof pattern-matching in xe-linux-distribution

[stormi]

The current implementation of xe-linux-distribution, based on sed, is rather fragile and often ends in that kind of error when the distro is unsupported:

[root@localhost Linux]# ./xe-linux-distribution 
sed: -e expression #1, char 103: invalid reference \2 on `s' command's RHS

We should implement the pattern matching in a more robust way while still portable of course.

I may give it a try sometime in the future...

[stormi]

Hmm, actually the error above probably only happens when it's trying an invalid pattern. The normal behaviour is to return nothing.

So it's less fragile than what I thought, but can easily be broken by future changes to the script. One just needs to add one invalid pattern somewhere, and this is not easily spotted during a PR review.