Adobe XMP SDK 4 beta

Adobe recently released a public beta of their new XMP SDK, which appears to be a huge improvement on the old SDK. I've compiled and run the example command line utilities on OS X (in this case, for reading metadata from a PDF), but haven't got round to testing the XMP writing functions yet. Hopefully, this should mean that applications like BibDesk should be able to read and write XMP metadata in the not-too-distant future.