Twenty Fourteen: fix low-contrast input elements in Firefox by explicitly setting `opacity: 1` for the placeholder text. Also brighten the border styles a bit. Props iamtakashi, fixes #25930.

git-svn-id: https://develop.svn.wordpress.org/trunk@26116 602fd350-edb4-49c9-b593-d223f7449a82
Twenty Fourteen: enhanced styles for logged-out comment form "required" mark and comment moderation text. Props iamtakashi, fixes #25932.

git-svn-id: https://develop.svn.wordpress.org/trunk@26117 602fd350-edb4-49c9-b593-d223f7449a82