Revisions: tweak how tickmarks are rendered, to play nice with browsers who always round subpixel values down (Safari, Opera).

Also, some IE tweaks.

Fixes #24736. Props adamsilverstein, markjaquith, ocean90.

git-svn-id: https://core.svn.wordpress.org/trunk@24768 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Revisions: RTL for [24761].

Props ocean90. See #24804.

git-svn-id: https://core.svn.wordpress.org/trunk@24769 1a063a9b-81f0-0310-95a4-ce76da25c4cd