bind: don't throw away result values with unknown type

The Java API wrapper generator use interface{} for Java classes
that no Go code references. Return values of unknown types are thrown
away, since they're effectively useless. Since the return values can
be used for nil checks and since casting of Java instances are
supported in CL 30095, this CL returns the naked *seq.Ref results
values instead.

Change-Id: I821b1c344a4c68c57fd34e2b655404e449de4c03
Reviewed-on: https://go-review.googlesource.com/30097
Reviewed-by: David Crawshaw <crawshaw@golang.org>

bind/java/ClassesTest.java

@@ -108,6 +108,12 @@ public class ClassesTest extends InstrumentationTestCase {
 		assertEquals("IOException message", Javapkg.IOExceptionMessage, exc.getMessage());
 	}
 
+	public void testUnknownType() {
+		GoObject o = new GoObject();
+		o.toString(); // Set this
+		assertTrue("GoObject.getClass not null", o.checkClass());
+	}
+
 	public void testInnerClass() {
 		Character.Subset s = new Character.Subset(""){};
 		Character.Subset s2 = new GoSubset("");