Arrows for revisions slider handle in two handled mode need attention

[adamsilverstein]

When viewing the revisions screen in 'compare two revisions' mode, the new graphics for the right hand slider handle introduced by 3.8/mp6 are slightly off (they are also slightly different in firefox vs chrome):

by comparison, the handles in 3.6 looked like this:

a small tweak to the css for the right handle gets us this, which is better (patch attached)

Another more serious regression is the handles in RTL mode - the placement is off (should be over tick mark) and the arrow directions are reversed - whoops! Fixing this one next:

[adamsilverstein]

correct arrow placement for two handles mode to handle

[iammattthomas]

In 26709:

Fix the positioning of arrow icons in the slider buttons in Revisions. See #26439.

[iammattthomas]

I went about this a slightly different way because there was some crufty/unnecessary CSS on those icons. Fixing the RTL issue is still outstanding.

[adamsilverstein]

correct placement & direction of slider handles in rtl mode

[adamsilverstein]

26439.2.diff​​: correct placement & direction of slider handles in rtl mode:

[iammattthomas]

In 26717:

Correct the direction of arrow icons when comparing revisions in RTL. Fixes #26439, props adamsilverstein.

[iammattthomas]

r26717 fixes the display bug for RTL, but it's working around the incorrectly generated RTL css. Barring a solution for that before freeze though, this fixes the immediate problem.