tree-optimization/107699 - missed &data._M_elems + _1 != &data._M_elems folding

tree-optimization/107699 - missed &data._M_elems + _1 != &data._M_elems folding

The following addresses a missed folding noticed in PR107699 that can
be fixed amending the existing &x + a != &x + b pattern to also handle
the case of only one side having a pointer plus.  I'm moving the
patterns next to related simpifications showing there'd be an existing
pattern matching this if it were not gated with an explicit single_use
constraint.  Note the new pattern also handles &x.a + a != &x.b, but
this hints at some unification / generalization opportunities here.

	PR tree-optimization/107699
	* match.pd (&a !=/== &a.b + c -> (&a - &a.b) !=/== c): New
	pattern variant.

	* gcc.dg/tree-ssa/pr107699.c: New testcase.