Add missing @ExportLibrary to PFunction

Author: fniephaus

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/builtins/objects/function/PFunction.java

@@ -38,12 +38,14 @@
 import com.oracle.truffle.api.CompilerDirectives.TruffleBoundary;
 import com.oracle.truffle.api.RootCallTarget;
 import com.oracle.truffle.api.Truffle;
+import com.oracle.truffle.api.interop.InteropLibrary;
 import com.oracle.truffle.api.interop.UnsupportedMessageException;
 import com.oracle.truffle.api.library.ExportLibrary;
 import com.oracle.truffle.api.library.ExportMessage;
 import com.oracle.truffle.api.nodes.RootNode;
 import com.oracle.truffle.api.source.SourceSection;
 
+@ExportLibrary(InteropLibrary.class)
 @ExportLibrary(PythonObjectLibrary.class)
 public class PFunction extends PythonObject {
     private static final Object[] EMPTY_DEFAULTS = new Object[0];