You will have to use the spine-c API to intersect rays against bounding box attachments on your skeleton. For that, you'll need the pointer to an spSkeleton stored by SkeletonRenderer/SkeletonAnimation. You can use SkeletonXXX::getSkeleton() for that.
With the spSkeleton in hand, you can then create a spSkeletonBounds to get the bounding boxes and polygons for a skeleton
spSkeletonBounds* bounds = spSkeletonBounds_create();
// each frame update the bounds after you've updated your skeleton
// last parameter will update the AABB for the entire skeleton
spSkeletonBounds_update(bounds, skeleton, 1);
// then use the bounds to do intersection testing, which will return
// the first bounding box attachment that contains the point (x, y).
// you can then look at the attachment to figure out what button
// was pressed
spBoundingBoxAttachment* attachment = spSkeletonBounds_containsPoint(bounds, x, y);
See the full API here spine-runtimes/SkeletonBounds.h at master
