Configuring out all XML support

[hendu]

Wishlist item:

It'd be nice to be able to disable all the XML support (saving, loading scenes, serialization, collada etc). I'm not using any of it, and the lib would likely be much smaller for that use case when built without those parts.

[hendu]

Preliminary numbers in: 500kb off the static library, 170kb off the shared lib.

[hendu]

Patch:

https://sourceforge.net/tracker/?func=d ... tid=540678

It only touches about 100 lines, smaller than I thought.

[hybrid]

Definitely a good idea, as we want to have everything configurable