Add one more line to render loop to avoid lines to "pop in" in case visible lines use less space than control dimensions
fixed handling of linespacing (was inconsistant and not working properly);
fixed juddering (now smooth scrolling possible even when using bigger fonts, faster scrolling speed and linespacing set)
Merge remote-tracking branch 'remotes/origin/BUG-4172-Text_in_scrollbox_pops_in_on_the_bottom_rather_than_scroll_in'
Merge branch 'master' of https://github.com/MediaPortal/MediaPortal-1
Merge branch 'refs/heads/master' into BUG-4118-Add_Padding_Property_To_Labels
Mantis #4188, #4189, #4190, #4191 and #2899

Fixes several glitches in the SkinEngine related to GUIButtonControl.cs usage that relies on rendering methods of GUIFadeLabel.cs

Even though these are independent issues, the fixes play hand in hand and cannot be seperated.

Also did some minor code cleanup in regards to remove inconsistent variable naming and redundant code that does nothing and was actually complicating fixing this issue.

Mantis #2899 should be fixed as a side effect as it's just one symptom of underlying defect.
Mantis #4193

Allow out of bounds rendering for a label when the label itself don't defined bounds.

This is for backwards compatibility with labels not having set width/height but still want to do a center alignment relatively to their text width. Meaning shifting it half the text length to the left for example (applies to watched count/watched percentage in current skins)