Bug 31933: fix 1.18 regression in Monobook sidebar: huge spacing between portlets...

Bug 31933: fix 1.18 regression in Monobook sidebar: huge spacing between portlets on IE 7 and IE 8/9 in compatibility view.

Followup r74966: drop some lines ported from MonoBook's old rtl.css. The floats don't seem to be needed and were breaking IE 7. Also contained some IE-Mac-related code that seems unnecessary since we no longer support that ancient browser. :)

Tested in:
* Firefox 7 LTR <- no regression
* Firefox 7 RTL <- no regression
* IE 6 LTR <- no regression
* IE 6 RTL <- no regression
* IE 7 LTR <- fixes regression
* IE 7 RTL <- no regression
* IE 8 regular LTR <- no regression
* IE 8 regular LTR <- no regression
* IE 8 regular RTL <- no regression
* IE 8 compatibility LTR <- fixes regression
* IE 8 compatibility RTL <- no regression
* IE 9 regular LTR <- no regression
* IE 9 regular RTL <- no regression
* IE 9 compatibility mode LTR <- fixes regression
* IE 9 compatibility mode RTL <- no regression