TAChart: Extract CreateLazIntfImage helper function

git-svn-id: http://svn.freepascal.org/svn/lazarus/trunk@40089 4005530d-fff6-0310-9dd1-cebe43e6787f
TAChart: Call inherited constructor from TSVGDrawer.Create

git-svn-id: http://svn.freepascal.org/svn/lazarus/trunk@40090 4005530d-fff6-0310-9dd1-cebe43e6787f