Introduce a new alignment option for latex strings:

//   ** Alignment rules
//   ------------------
//  The TText alignment rules apply to the TLatex objects with one exception
//  concerning the vertical alignment:
//  If the vertical alignment = 1 , subscripts are not taken into account
//  if the vertical alignment = 0 , the text is aligned to the box surrounding
//                                  the full text with sub and superscripts


git-svn-id: http://root.cern.ch/svn/root/trunk@440 27541ba8-7e3a-0410-8455-c3a389f83636