Hudson not building with JSON-C

[robe]

I think we want it to build with JSON-C so it can test s ST_GeomFromGeoJSON.

I'm also wondering if this is not something we should give a stronger WARNING about since this is becoming a very popular function for web application developers and I can see many package managers overlooking this function because all their regress tests will pass since the function test will just be left out.

[chodgson]

I've added json-C 0.9 to the buildbot compile and regression testing.