Fixes #647: Added an implicit conversion operator from `memory::mappe…

…d::span_pair_t<T>` to a pair of `region_t`'s (i.e. with type erasure, as opposed to casting into a pair of `span<T>`'s

src/cuda/api/memory.hpp

@@ -121,6 +121,7 @@ struct span_pair_t {
 	span<T> host_side, device_side;
 
 	constexpr operator ::std::pair<span<T>, span<T>>() const { return { host_side, device_side }; }
+	constexpr operator ::std::pair<region_t, region_t>() const { return { host_side, device_side }; }
 };
 
 /**