SynEdit: fix matching bracket, broken in revision 39692 Issue 0023556

git-svn-id: http://svn.freepascal.org/svn/lazarus/trunk@39719 4005530d-fff6-0310-9dd1-cebe43e6787f
SynEdit: matching bracket, tests

git-svn-id: http://svn.freepascal.org/svn/lazarus/trunk@39720 4005530d-fff6-0310-9dd1-cebe43e6787f