* NEW: '_operators' interface has been renamed as '_operator'.
* NEW: Arithmetic operators now can be applied on two objects with
  different classes. One at least must implement the '_operator' interface.
* NEW: Each class that implements the '_operator' interface has now an 
  automatic priority that follows the load order. When a binary operator 
  has two objects that implement two different '_operator' interface, the
  one having the highest priority is used.
* NEW: Implementing all methods in the '_operators' interface is not 
  mandatory anymore. If one method is not implemented, then it is replaced
  by a function that raises a 'Type mismatch' error.

[GB.GSL]
* NEW: Matrix arithmetic has been implemented.
* NEW: Matrix.Determinant() method.
* NEW: Matrix.Invert() method.
* NEW: Matrix.Transpose() method.
* NEW: Matrix _call special method multiplies a matrix by a vector.
* NEW: Vector <-> Array conversion.


git-svn-id: svn://localhost/gambas/trunk@4946 867c0c6c-44f3-4631-809d-bfa615b0a4ec