Fix incorrect variable setters being generated when wrapping
reference member variables. A setter is no longer generated if the
type of the reference member variable is non-assignable.
Fixes#2866
A struct/class that contains a non-assignable member variable is
actually assignable itself. Only non-static members, not static members,
contribute to the containing class being non-assignable.
Recent regression fix from a few commits back.
A class that does not have an explicit assignment operator does not
have an implicit assignment operator if a member variable is not
assignable. Similarly should one of the base classes also not be
assignable. Detection of these scenarios has been fixed so that when
wrapping a variable that is not assignable, a variable setter is not
generated in order to avoid a compiler error.
Template instantiation via %template is required in order for this to
work for templates that are not assignable.
Closes#1416
William S Fulton