Fix a bug in how comparison instructions are handled: the 'a' intruction field

was ignored.  Includes new test case.

src/test/java/lua/LuaJTest.java

@@ -43,6 +43,10 @@ public class LuaJTest extends TestCase {
 		runTest( "test7" );
 	}
 	
+	public void testCompare() throws IOException, InterruptedException {
+		runTest( "compare" );
+	}
+	
 	public void testUpvalues() throws IOException, InterruptedException {
 		runTest( "upvalues" );
 	}