Enlarge maximum secondary allocation size for files

The maximum secondary allocation size for data storage, normal index and upper index for an Adabas file are file attributes. Their values are kept in the FCB.
Unfortunately, there's only a halfword (2 bytes) provided for those values and the values are interpreted as RABN blocks. Considering the file sizes possible nowadays, this is not an up to date solution any more.
4 bytes for the values and the alternative supply of sizes in units of cylinders is a necessary and - for the rest of the Adabas world - also uniform solution.
The FCB fields and the connected functionality should get enhanced accordingly.