Sablotron and Autotools?

[Robert J. Hansen]

For a project I'm working on, I need a crossplatform XML inspector.   
GDOME2 is out because it doesn't work on OS X, so we're instead  
looking at Sablotron.  Looking at the Autoconf Archive I don't see  
any m4 macros for Sablotron, nor does it come with a pkg-config file.

What is the canonical way to test for the existence of libsablot with  
autoconf 2.60?