[RFA/www] Mention Ada in list of supported languages

[Joel Brobecker]

> A coworker mentioned to me this week that Ada is not mentioned
> in the list of languages supported by the debugger. I was wondering
> if we could add this in the general description of GDB on the main
> page. I took the opportunity to re-order by alphabetic order. I'm
> completely open to any other ordering however.

Thanks to everyone who provided their feedback - no-one objected
so I checked the change in.

Thanks,
-- 
Joel