1.0.27.6: Make alien-type-class definition work from outside sb-alien.

1.0.27.6: Make alien-type-class definition work from outside sb-alien.

  Added a slot to the alien-type-class structure to hold the name of
the structure for the class.

  Added the class structure name as a parameter to
create-alien-type-class-if-necessary in order to populate the slot in
the new alien-type-class structure.

  Changed define-alien-type-class to look up included alien type
defstruct names in the alien-type-class for the included type rather
than construct it via SYMBOLICATE (thus breaking the requirement that
all uses of define-alien-type-class be in the sb-alien package).