Fix portability issue with ArrayRef initializer overloading

Some compilers (in particular the Fujitsu compilers that are
derived from an earlier version of Clang) will not allow
overloading functions where one version uses a pointer to a
type, and the other a vector iterator to the same type - likely
because they have implemented iterators with pointers.
Regardless of what the C++ standard says, we need this working
on K computer, so this patch replaces the overloaded
initializers with non-member functions that create an ArrayRef
or ConstArrayRef either from pointers, an array,
or iterators.

Change-Id: I4c4e327c869920cc08e3f955e88cb3a5b28c7e87