Uff, I hope this is the last attempt to fix pixel base GUI: it looks like ascent for a font in X11 includes some additional pixels above
the maxium gluph's height. A lot of layout hints have toppad 0 because of this (?). With CoreText/Quartz 2D I do not have these additional
pixels and a lot of widgets (with text) have 2-3 pixels shifted text. Since I can not fix them all, I have to add these pixels when
calculating font metrics. This seems to fix all text buttons, check boxes, radio buttons, tooltips, tree view, etc.


git-svn-id: http://root.cern.ch/svn/root/trunk@47078 27541ba8-7e3a-0410-8455-c3a389f83636