LCL, DbImage implements loading stream directly if it doesn't have a known header, WriteHeader property to make writing img header optional

git-svn-id: http://svn.freepascal.org/svn/lazarus/trunk@43779 4005530d-fff6-0310-9dd1-cebe43e6787f
LazReport, handle db image streams the same way as dbimage

git-svn-id: http://svn.freepascal.org/svn/lazarus/trunk@43780 4005530d-fff6-0310-9dd1-cebe43e6787f