random memory leak fixes

random memory leak fixes

This fixes leaks discovered checking whether I introduced new ones
with the last vectorizer changes.

2020-10-09  Richard Biener  <rguenther@suse.de>

	* cgraphunit.c (expand_all_functions): Free tp_first_run_order.
	* ipa-modref.c (pass_ipa_modref::execute): Free order.
	* tree-ssa-loop-niter.c (estimate_numbers_of_iterations): Free
	loop body.
	* tree-vect-data-refs.c (vect_find_stmt_data_reference): Free
	data references upon failure.
	* tree-vect-loop.c (update_epilogue_loop_vinfo): Free BBs
	array of the original loop.
	* tree-vect-slp.c (vect_slp_bbs): Use an auto_vec for
	dataref_groups to release its memory.