Make dump_ranger routines externally visible.

There was an inline extern declaration for dump_ranger that was a bit of
a hack.  I've removed it in favor of an actual prototype.  There are
also some trivial changes to the dumping code in the path solver.

gcc/ChangeLog:

	* gimple-range-path.cc (path_range_query::path_range_query): Add
	header.
	(path_range_query::dump): Remove extern declaration of dump_ranger.
	* gimple-range-trace.cc (dump_ranger): Add DEBUG_FUNCTION marker.
	* gimple-range-trace.h (dump_ranger): Add prototype.