SynEdit: Fixed painting highlight frame-borders. (do not paint extra left/right borders)

git-svn-id: http://svn.freepascal.org/svn/lazarus/trunk@43424 4005530d-fff6-0310-9dd1-cebe43e6787f
SynEdit: prepare extra highlight for lines starting a fold

git-svn-id: http://svn.freepascal.org/svn/lazarus/trunk@43425 4005530d-fff6-0310-9dd1-cebe43e6787f