fpvectorial: Adds support for vertical stacks in MathML and improves the formula infrastructure in general

git-svn-id: http://svn.freepascal.org/svn/lazarus/trunk@41465 4005530d-fff6-0310-9dd1-cebe43e6787f
fpvectorial: Vertical formulas look nicer with a smaller vertical spacing

git-svn-id: http://svn.freepascal.org/svn/lazarus/trunk@41466 4005530d-fff6-0310-9dd1-cebe43e6787f