fcl-db: bufdataset: when data are written to BLOB field (using TBufBlobStream) assign new write blob buffer to BLOB field in record buffer. So new data are there before Post.
(setting FieldByName('blob').AsString:='...' does not save data to field until record is posted)

git-svn-id: http://svn.freepascal.org/svn/fpc/trunk@26604 3ad0048d-3df7-0310-abae-a5850022a9f2