Requests for comment/Inline diffs

I propose to integrate inline (one-column) diffs from MobileFrontend into MediaWiki core. Mobile screens are smaller so standard side-by-side diffs aren't good. To address this, the mobile team developed a new diff mode. Example diff.

Implementation details
Inline diffs use existing core diff code as much as possible, therefore the code is very compact and has the same performance characteristics as two-column diffs.