Push math nodes onto mathArray individually to avoid problem in IE < 9 where push.apply doesn't work on a nodeList.  Also, avoid duplicate elements in the array by checking for namespace prefixes.  This needs to work for both HTML and XHTML.  Resolves issue #672.
Merge remote-tracking branch 'dpvc/issue672' into v2.3-latest
Merge branch 'v2.3-latest'