Rename relation oracle and API.

Rename relation oracle and API.

With more oracles incoming, rename the range_query oracle () method to
relation (), and remove the redundant 'relation' text from register and query
methods, resulting in calls that look like:
  relation ()->record (...)   and
  relation ()->query (...)

	* gimple-range-cache.cc (ranger_cache::dump_bb): Use m_relation.
	(ranger_cache::fill_block_cache): Likewise
	* gimple-range-fold.cc (fur_stmt::get_phi_operand): Use new names.
	(fur_depend::register_relation): Likewise.
	(fold_using_range::range_of_phi): Likewise.
	* gimple-range-path.cc (path_range_query::path_range_query): Likewise.
	(path_range_query::~path_range_query): Likewise.
	(ath_range_query::compute_ranges): Likewise.
	(jt_fur_source::register_relation): Likewise.
	(jt_fur_source::query_relation): Likewise.
	(path_range_query::maybe_register_phi_relation): Likewise.
	* gimple-range-path.h (get_path_oracle): Likewise.
	* gimple-range.cc (gimple_ranger::gimple_ranger): Likewise.
	(gimple_ranger::~gimple_ranger): Likewise.
	* value-query.cc (range_query::create_relation_oracle): Likewise.
	(range_query::destroy_relation_oracle): Likewise.
	(range_query::share_oracles): Likewise.
	(range_query::range_query): Likewise.
	* value-query.h (value_query::relation): Rename from oracle.
	(m_relation): Rename from m_oracle.
	* value-relation.cc (relation_oracle::query): Rename from
	query_relation.
	(equiv_oracle::query): Likewise.
	(equiv_oracle::record): Rename from register_relation.
	(relation_oracle::record): Likewise.
	(dom_oracle::record): Likewise.
	(dom_oracle::query): Rename from query_relation.
	(path_oracle::record): Rename from register_relation.
	(path_oracle::query): Rename from query_relation.
	* value-relation.h (*::record): Rename from register_relation.
	(*::query): Rename from query_relation.