Build tracequery to scan for tracepoints

Build tracequery to scan for tracepoints

	* session.h (systemtap_session): add tracepoint_derived_probes
	* buildrun.cxx (make_tracequery): New - builds a kernel module that
	hijacks the tracepoint declarations, so we can query debuginfo.
	* buildrun.h: declare above
	* tapsets.cxx (tracepoint_builder): New builder for tracepoint
	probes.  For now it just handles the initialization to build the
	tracequery kernel module.