Minor cleanups to solver.

Minor cleanups to solver.

These are some minor cleanups and renames that surfaced after the
hybrid_threader work.

gcc/ChangeLog:

	* gimple-range-path.cc
	(path_range_query::precompute_ranges_in_block): Rename to...
	(path_range_query::compute_ranges_in_block): ...this.
	(path_range_query::precompute_ranges): Rename to...
	(path_range_query::compute_ranges): ...this.
	(path_range_query::precompute_relations): Rename to...
	(path_range_query::compute_relations): ...this.
	(path_range_query::precompute_phi_relations): Rename to...
	(path_range_query::compute_phi_relations): ...this.
	* gimple-range-path.h: Rename precompute* to compute*.
	* tree-ssa-threadbackward.c
	(back_threader::find_taken_edge_switch): Same.
	(back_threader::find_taken_edge_cond): Same.
	* tree-ssa-threadedge.c
	(hybrid_jt_simplifier::compute_ranges_from_state): Same.
	(hybrid_jt_state::register_equivs_stmt): Inline...
	* tree-ssa-threadedge.h: ...here.