The following testcase is optimized with char/unsigned char/signed char,
but not with std::byte.  The following patch fixes that.  Didn't use
INTEGRAL_TYPE_P because bswapping bools is just too weird.

2020-03-31  Jakub Jelinek  <jakub@redhat.com>

	PR tree-optimization/94403
	* gimple-ssa-store-merging.c (verify_symbolic_number_p): Allow also
	ENUMERAL_TYPE lhs_type.

	* g++.dg/tree-ssa/pr94403.C: New test.