When parsing a new element, clear the maps holding the unparsed attribute we have seen.

This because these maps keep pointers to the name of the attributes object that gets recycled
for every element (and their name is deallocated when recycled)


git-svn-id: https://svn.apache.org/repos/asf/xerces/c/trunk@175621 13f79535-47bb-0310-9956-ffa450edef68