Inconsistent use of : and :: for styling pseudo elements

[tomatic]

Dawn makes inconsistent use of : and :: for styling pseudo elements like after, sometimes even within the same CSS file.

Dawn 15.0.2 currently has 34 instances of ::after and 81 instances of the incorrect :after.

While modern browsers apparently accept both, the correct syntax for pseudo elements is the double colon, the single colon is for pseudo classes. If anything, the usage should at least be consistent throughout the theme.