Added shared_ptr aliasing move constructor.

Signed-off-by: Gavin Lambert <github@mirality.co.nz>

test/Jamfile.v2

@@ -34,6 +34,7 @@ import testing ;
           [ run shared_ptr_alias_test.cpp ]
           [ run shared_ptr_rv_test.cpp ]
           [ run shared_ptr_move_test.cpp ]
+          [ run shared_ptr_alias_move_test.cpp ]
           [ compile-fail shared_ptr_pv_fail.cpp ]
           [ run sp_unary_addr_test.cpp ]
           [ compile-fail scoped_ptr_eq_fail.cpp ]