This commit implements detection of exponential entity

expansions inside the scanner code.  This is only done when a
security manager instance has been registered with the parser by
the application.  The default number of entities which may be
expanded is 50000; this appears to work very well for SAX, but DOM
parsing applications may wish to set this limit considerably lower.


git-svn-id: https://svn.apache.org/repos/asf/xerces/c/trunk@174905 13f79535-47bb-0310-9956-ffa450edef68