Make the "Developers" link in the footer not-'external'

Linker::makeExternalLink() adds class="external" to the link, which
results in an itty-bitty arrow being rendered next to it on Vector.
We do not want that.

Also don't pass the contents of the 'wikimedia-developers' message
through Title::newFromText()->__toString(), no idea why that was done.

Change-Id: Id650073e7e0a3ca1800c8a4398321750413e0db8
Merge "Make the "Developers" link in the footer not-'external'"