The 'Xml_node::differs_from' method takes the constructor arguments
(addr, size) for a byte-wise comparison whereas 'with_raw_node'
restricts the byte range to the actual XML tags. In cases where
the XML start tag is preceeded by whitespace, both ranges can differ.
Since the 'differs_from' method is meant for comparing actual XML
nodes - not any whitespace around them - whitespace should be ignored
on both operands.
Issue #5029