SHP provider: file pointer overflow in the case of large DBF files

[danstoica]

The following code is faulty for large DBF files (as number of records) and large record size:

SetFilePointer?64((FdoInt?64)(m_nRecordStart + (nRecord * m_DBFHeader.wRecordSize)))

All the integers involved in the file pointer values are Int32 thus the result is an int32 (max_int= 2147483647). In the case of recordNumber = 700000 a record size of 3070 will be enough to result into a negative number for the file pointer.