Move to the next node in the data steam created by open thus allowing the node's properties to be queried via the Reader accessors. Return 0 on successful read, 1 if there are no more nodes to read, and a negative number otherwise. Note that each call to advanceToNextNode invalidates strings and data structures returned when Reader accessors were called for the "prior node". E.g., the pointer returned from nodeName for this node will not be valid once advanceToNextNode is called. Note that the reader will not be on a valid node until the first call to advanceToNextNode after the reader is opened.