Default methods should not be bound

[headius]

In jruby/jruby#6714 we discovered that jnr-ffi is attempting to bind a getsockoptInt method to the same named-C function, which of course fails.

The problem here is due to JRuby's BasicSocket using an interface for jnr-ffi that has default methods (utility wrappers around the other methods) which are not intended to be bound to a native endpoint. The java.lang.Proxy logic in Java 8-15 provides no way to invoke the default method, so we proceed to attempt to bind it as a native call.

Unfortunately the fixes for this are pretty heinous. This SO post seems to indicate that there is no clean way to fix it until Java 16. The only option for us in Java 8 would be to rework how the interface proxy gets initialized, passing in a Lookup that can access and call the default method.

https://stackoverflow.com/questions/26206614/java8-dynamic-proxy-and-default-methods

For now we will remove the default methods in JRuby, but this needs a proper fix in jnr-ffi.