MetaImpl.MetaColumn doesn't follow JDBC spec

MetaImpl.MetaColumn which is used as a record for DatabaseMetadata#getColumns doesn't follow JDBC spec:

several fields have incorrect types:

• bufferLength should be an int (based on name, but not clarified in spec)
• sqlDataType should be an int
• sqlDatetimeSub should be an int
• sourceDataType should be a short

some fields also have incorrect nullability:

• columnSize, charOctetLength and numPrecRadix can be null when they don't apply to their specific types
• isNullable, isAutoincrement and isGeneratedcolumn should be a nullable fields (although they are not primitive fields), with value set to the empty string if undefined.