FIX: array.vec.make_xxxyy now works for all sizes (incl. yy=3 which requ...

...ires padding); deliberately removed default values (feel free to add again)

Closes #28

IMPORTANT: I didn't run the tests. Removing the default values might break some applications.

Rationale for removing the default values: It's just too easy to create the wrong vector size if all parameters have default values.