XML parsing in corebase

[Stefan Bidi]

Now that the first version of corebase has been release, I start
looking into what will and will not be included in the next release.
While I was going through the Apple documentation for Core Foundation
I noticed that the whole XML parsing capability has been deprecated is
OS X 10.8.  So CFXMLParser, CFXMLTree and CFXMLNode are no deprecated.

My question to anyone interested in this project is if you would still
like to see these types implemented at some point?  If not, I will
remove them from the source tree.  They are just stubs, at the moment.

Stef