py: Allow retrieving a function's __name__.

Disabled by default.  Enabled on unix and stmhal ports.

tests/basics/fun_name.py

@@ -0,0 +1,16 @@
+def Fun():
+    pass
+
+class A:
+    def __init__(self):
+        pass
+    def Fun(self):
+        pass
+
+try:
+    print(Fun.__name__)
+    print(A.__init__.__name__)
+    print(A.Fun.__name__)
+    print(A().Fun.__name__)
+except AttributeError:
+    print('SKIP')