irc:// scheme considered invalid

_From [Heiko.Ru...@googlemail.com](https://code.google.com/u/114249341487134308671/) on August 12, 2013 08:25:57_

PROBLEM:
```
WARNING: how_to.epub/OEBPS/ch20.html(4): use of non-registered URI schema type in href: irc://irc.freenode.net 
```

Give a brief description of the problem:
epubcheck warns that this schema "irc" is not registered

That scheme seems to be officially registered with IANA ( http://en.wikipedia.org/wiki/URI_scheme ) and at least some ePub readers like Aldiko on Android fire an Irc-client (when it is present).

Please consider adding this.

_Original issue: http://code.google.com/p/epubcheck/issues/detail?id=296_