Expose the memory allocation functionalities of DOMDocumentImpl through the DOMMemoryManager interface; this removes dangerous casts in the operator new and allows to tune the size of the memory chunks (jira# 1475)

git-svn-id: https://svn.apache.org/repos/asf/xerces/c/trunk@357986 13f79535-47bb-0310-9956-ffa450edef68