Function: eieiomt-add

Add to METHOD-NAME the forms METHOD in a call position KEY for CLASS.
METHOD-NAME is the name created by a call to `defgeneric'.
METHOD are the forms for a given implementation.
KEY is an integer (see comment in eieio.el near this function) which
is associated with the :static :before :primary and :after tags.
It also indicates if CLASS is defined or not.
CLASS is the class this method is associated with.