This is part of the series started by D68484.
This pass connects llvm.noalias.decl to llvm.noalias, llvm.provenance.noalias
and llvm.noalias.copy.guard intrinsics when those are associated with the
unknown function scope and depend on the same alloca object. The connection
allows a refinement of the noalias information for those intrinsics, resulting
in better code.
Note: this is a stable point and tests should run fine with the patches applied up to this point.