SynEdit: speed up large operations (search replace)

git-svn-id: http://svn.freepascal.org/svn/lazarus/trunk@43763 4005530d-fff6-0310-9dd1-cebe43e6787f
SynEdit: speed up large operations (search replace) / fix

git-svn-id: http://svn.freepascal.org/svn/lazarus/trunk@43764 4005530d-fff6-0310-9dd1-cebe43e6787f