Add isHashable to P[Builtin]Method

Author: msimacek

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/builtins/objects/method/PBuiltinMethod.java

@@ -68,6 +68,11 @@ public boolean isCallable() {
         return true;
     }
 
+    @ExportMessage
+    boolean isHashable() {
+        return true;
+    }
+
     @ExportMessage
     protected long hashWithState(@SuppressWarnings("unused") ThreadState state) {
         return PythonAbstractObject.systemHashCode(this.getSelf()) ^ PythonAbstractObject.systemHashCode(this.getFunction());

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/builtins/objects/method/PMethod.java

@@ -80,6 +80,11 @@ protected boolean hasSourceLocation(@CachedLibrary("this.function") InteropLibra
         return lib.hasSourceLocation(function);
     }
 
+    @ExportMessage
+    boolean isHashable() {
+        return true;
+    }
+
     @ExportMessage
     protected long hashWithState(@SuppressWarnings("unused") ThreadState state) {
         return PythonAbstractObject.systemHashCode(this.getSelf()) ^ PythonAbstractObject.systemHashCode(this.getFunction());