On-the-fly spellchecking in Kate

Christoph just added an awesome and long awaited feature: on-the-fly spellchecking. 'Kate's xml highlighting files now have an additional attribute in the itemData section: spellChecking="true/false". C++ comments and strings can be spellchecked now :) Same for all other languages such as Latex. Really big thanks to Michel Ludwig for the patch, good work! Screenshot for latex highlighting: