fix memory leaks

fix memory leaks

This fixes various vec<> memory leaks as discovered compiling 521.wrf_r.

2021-02-02  Richard Biener  <rguenther@suse.de>

	* gimple-loop-interchange.cc (prepare_data_references):
	Release vectors.
	* gimple-loop-jam.c (tree_loop_unroll_and_jam): Likewise.
	* tree-ssa-loop-im.c (hoist_memory_references): Likewise.
	* tree-vect-stmts.c (vectorizable_condition): Do not
	allocate vectors.
	(vectorizable_comparison): Likewise.