autoconf

I submitted another patch to libxr mailing list just now, it is used to fix the small bug in `configure.ac', so that libxr will generate a correct `xr-config.h' when a JSON run-time is found.

I started to contribute to libxr since last Dec., and I consider it my first real participation in OSS development. Yes I've previous experiences writting test suites for openhpi, openipmi and openwsman, during my internship. But frankly speaking, I had few feelings of joy then.

I enjoyed the discussion in E-mail, and I'd like to thank the author of libxr, who gave me a lot of helps.