fcl-db: bufdataset: fixes bug when saving of BLOB data using SaveToFile or SaveToStream in dfBinary format.(instead of BLOB data only pointer to "BLOB buffer record" is saved)
Format of saved data is changed as follows:
- Identification (start of file) changes from "BinBufDataset" (OLD version named 1.0) to "BinBufDataSet" (NEW version named 2.0)
- Just after Identification ("BinBufDataSet") is written one byte indicating version (for now it is 20 as 2.0)
- FieldDefs are saved in same format as in OLD format (nothing chages)
- Record header is saved in same format as in OLD format (nothing chages)
- Record data are saved field by field, where each field begins with 4 bytes indicating length of data, followed by data (here is used TField.AsBytes to get actual data)

Backward compatibility is keept in reading OLD format
When saving NEW format is always used


git-svn-id: http://svn.freepascal.org/svn/fpc/trunk@25333 3ad0048d-3df7-0310-abae-a5850022a9f2