Undefined Errno::EPROTO and the like raises NameError

Hi,

I just run into the problem, that certain System Call Errors aren't 
defined depending on the platform. I tested on a platform, where 
Errno::EPROTO is not defined. If I code something like

begin
#...
rescue Errno::Foo, Errno::Bar, Errno::EPROTO
#...
rescue Errno::Baz
end

a NameError "uninitialized constant Errno::EPROTO" is raised. So, it's 
not possible to write platform agnostically rescue cases.

EPROTO is set like this:

#ifdef EPROTO
    set_syserr(EPROTO, "EPROTO");
#endif

Perhaps it would be a good idea, to at least set the not defined errors 
(which Ruby checks for) to nil, to avoid the raised NameErrors?

-- 
Florian Frank