SynEdit: user highlight, find longest match

git-svn-id: http://svn.freepascal.org/svn/lazarus/trunk@42716 4005530d-fff6-0310-9dd1-cebe43e6787f
Test: fixed expectation for checkbox background color

git-svn-id: http://svn.freepascal.org/svn/lazarus/trunk@42717 4005530d-fff6-0310-9dd1-cebe43e6787f