Have v_remove operate on a single element

Have v_remove operate on a single element

This way it can work like a generalized pop(), and the caller
can use/free the element as desired. Removing a range has no
clean way to return the elements to the caller, other than
packaging up the results into a new vector perhaps.

Later we could add a v_erase() that works on a range and frees
the elements, like the C++ vector::erase(). Or call it v_delete()
like Vectors in Ada.