Allow comments in grammar rules. Start working on Python3 class (not

finished). More test organization.

test/simple_source/def/01_class.py

@@ -1,2 +1,15 @@
+# Tests:
+#
+# For Python3:
+#   classdef ::= LOAD_BUILD_CLASS mkfunc LOAD_CONST CALL_FUNCTION_2 designator
+#   mkfunc ::= LOAD_CONST LOAD_CONST MAKE_FUNCTION_0
+
+# For Python2:
+#   classdef ::= LOAD_CONST expr mkfunc CALL_FUNCTION_0 BUILD_CLASS designator
+#   mkfunc ::= LOAD_CONST MAKE_FUNCTION_0
+
 class A:
     pass
+
+# class B(Exception):
+#     pass

test/simple_source/def/02_def.py

@@ -0,0 +1,15 @@
+def x0():
+    pass
+
+def x1(a):
+    pass
+
+
+def x2(a=5):
+    pass
+
+def x3(a, b, c=5):
+    pass
+
+def x4(a, b=5, **c):
+    pass

test/simple_source/def/def0.py

@@ -1,2 +0,0 @@
-def x0():
-    pass

test/simple_source/def/def1.py

@@ -1,2 +0,0 @@
-def x1(a):
-    pass