3.6 omit END_FINALLY sometimes

Fixes #182

test/simple_source/bug36/02_tryfinally_return.py

@@ -0,0 +1,6 @@
+# Python 3.6 sometimes omits END_FINALLY. See issue #182
+def foo():
+    try:
+        x = 1
+    finally:
+        return

uncompyle6/parsers/parse36.py

@@ -106,6 +106,10 @@ class Python36Parser(Python35Parser):
                              COME_FROM_FINALLY suite_stmts_opt END_FINALLY
         except_suite_finalize ::= SETUP_FINALLY returns
                                   COME_FROM_FINALLY suite_stmts_opt END_FINALLY _jump
+
+        stmt ::= tryfinally_return_stmt
+        tryfinally_return_stmt ::= SETUP_FINALLY suite_stmts_opt POP_BLOCK LOAD_CONST
+                                   COME_FROM_FINALLY
         """
 
     def customize_grammar_rules(self, tokens, customize):

uncompyle6/semantics/customize3.py

@@ -507,6 +507,9 @@ def customize_for_version3(self, version):
                 'try_except36':   ( '%|try:\n%+%c%-%c\n\n', 1, 2 ),
                 'except_return':  ( '%|except:\n%+%c%-', 3 ),
                 'unpack_list':    ( '*%c', (0, 'list') ),
+                'tryfinally_return_stmt':
+                      ( '%|try:\n%+%c%-%|finally:\n%+%|return%-\n\n', 1 ),
+
                 'call_ex' : (
                     '%c(%p)',
                     (0, 'expr'), (1, 100)),