Add an explicit targets declaration for mediawiki.inspect & $.byteLength

Add an explicit targets declaration for mediawiki.inspect & $.byteLength

Jon Robson said[1] he'd be interested in making mediawiki.inspect usable on
the mobile site by specifying both mobile & desktop targets explicitly in the
resource declaration. That's what this patch does. The cost to this is very
minimal because the module is never loaded by default. mw.loader.inspect()
wraps the call to the inspector with an mw.loader.using() call that causes the
module to be retrieved. It is not retrieved otherwise.

[1]: http://lists.wikimedia.org/pipermail/wikitech-l/2013-October/072381.html

Change-Id: I7cf292d3b8fb554bd1fc2143ca45399efccb70aa