The move detection flags alter both the alignment of the line numbers

and code, which can cause some confusion during review. Much of this was

due to some old CSS that impacted the line number cell, and there not

being enough room for the move range line in the code cell.
The CSS has been fixed to address all this. We still show a 4px move

range line, but now it's spread across the line number header and code

cell, 3px in the header and 1px in the cell. This takes advantage of the

spacing we already have available in both cells without worrying about

bumping right up against any text, or having to increase the default

padding in either cell.

Tested in Chrome and Firefox. Checked for perfect pixel alignment in the

cells.