geom: delete rval constructors for samplers

Samplers tend to hold a const reference to the relevant data and so we
want to ensure it's not possible to inadvertantly pass in a reference to
data that is going out of scope.

geom/aabb.hpp

@@ -148,6 +148,7 @@ namespace cruft::geom::sample {
     public:
         using shape_type = aabb<S,T>;
 
+        volume (shape_type&&);
         volume (shape_type const &target):
             m_target (target)
         { ; }

geom/ellipse.hpp

@@ -152,6 +152,7 @@ namespace cruft::geom::sample {
     public:
         using shape_type = ellipse<2,T>;
 
+        volume (shape_type &&) = delete;
         volume (shape_type const &target):
             m_target (target)
         { ; }

geom/sample/volume.hpp

@@ -49,7 +49,10 @@ namespace cruft::geom::sample {
     template <typename ShapeT>
     class volume {
     public:
-        explicit volume (ShapeT const &target):
+        using shape_type = ShapeT;
+
+        explicit volume (shape_type&&) = delete;
+        explicit volume (shape_type const &target):
             m_target (target)
         { ; }
 
@@ -82,6 +85,7 @@ namespace cruft::geom::sample {
     public:
         using shape_type = extent<S,T>;
 
+        explicit volume (shape_type&&) = delete;
         explicit volume (shape_type const &target):
             m_target (target)
         { ; }