[2/2] Add store merging unit tests

[2/2] Add store merging unit tests

	* gimple-ssa-store-merging.c: Include selftest.h
	(verify_array_eq): New function.
	(verify_shift_bytes_in_array): Likewise.
	(verify_shift_bytes_in_array_right): Likewise.
	(verify_clear_bit_region): Likewise.
	(verify_clear_bit_region_be): Likewise.
	(store_merging_c_tests): Likewise.
	* selftest.h (store_merging_c_tests): Declare prototype.
	* selftest-run-tests.c (selftest::run_tests): Run
	store_merging_c_tests.

From-SVN: r241971