Added tests for random access by index in pack operators.
Added tests for random access by index in pack operators.

Checking creating subpacks by random access by index, using
the (...) operator in both declpack and templify syntaxes.

// access based playing with types in the pack, templify style
template<typename... T>
auto e5(T...)
    -> templify((someclass) (T...){}(2,1,2,1,2,1,2,1));

// access based playing with types in the pack, declpack style
template<typename... T>
auto e6(T...)
    -> declpack( ((T...){}(3,3,3))
		  |= clause::ample::as_template_of<someclass> );

irrequietus/clause,irrequietus/clause