The unsigned integers that would previously be interpreted as negative
values are now correctly converted into their corresponding avro
values. Due to a limitation in the Avro file format, 64-bit unsigned
integers cannot be represented in their unsigned form.
Since both the signed and unsigned versions of a 32-bit integer cannot fit
into a single Avro int, the type for these was changed to long. This is a
backwards incompatible change which means files generated with older
versions will not convert unsigned values correctly.
72d9e41ccb