Compatibility: 1.0+
Expects: AH    21H
DS:DX address of an opened FCB
Returns: AL    0 if read was successful (and DTA is filled with data)
1 if EOF was reached and no data was read
2 if DTA + FCB RecSize would overrun a segment (no read)
3 if EOF and a partial record was read (padded with 0s)
Info: Sets FCB curBlk and curRec to the agree with randomRec then reads
recSize bytes from the specified file address, placing the data
into memory starting at the DTA.

Notes:   Be sure to set recSize to the record length and randomRec in
the FCB to the desired record number.

See Also: Fn 3fH (read file via handle)
- -

DOS Fn 21H: Read Random File Record