Make Language::fetchLanguageName lowercase its first argument.

Currently Language::fetchLanguageName( 'en-GB' ) returns false as
it expects 'en-gb'. Given that technically speaking, 'en-GB'
is the canonical form, I don't think this is a good thing.

Changed function to lowercase its argument. There's no
Language object handy, so I just used strtolower (since language
codes are always ascii, that shouldn't matter)

Change-Id: Iba1f581bf2d6d2b26a14f9f80699d8eeb5d724d6
Merge "Make Language::fetchLanguageName lowercase its first argument."