At some point in the past, a merge from release-2.0.x to master deleted a bunch

of style rules. Christian fixed most of these, but there was one that didn't

make it, which set the box-sizing mode for file attachments. This wasn't

immediately obvious because things still looked correct, except when the

caption editor for file attachments was opened, it was 2px less wide than the

box it was supposed to be flush with.

Opened the file attachment caption editor and saw that everything aligned

nicely.