This icon is used to represent an issue that is pending verification by

the reviewer. It has the same shape as an open issue, with a more

subdued (but still present) color, and arrows pointing in opposite

directions to indicate a back-and-forth between reviewer and developer.
A .rb-icon-issue-verifying CSS class has been added for using this icon.

Tested in the browser by replacing the icon's CSS class on an open issue.