py/runtime: Allow multiple *args in a function call.

This is a partial implementation of PEP 448 to allow unpacking multiple
star args in a function or method call.

This is implemented by changing the emitted bytecodes so that both
positional args and star args are stored as positional args.  A bitmap is
added to indicate if an argument at a given position is a positional
argument or a star arg.

In the generated code, this new bitmap takes the place of the old star arg.
It is stored as a small int, so this means only the first N arguments can
be star args where N is the number of bits in a small int.

The runtime is modified to interpret this new bytecode format while still
trying to perform as few memory reallocations as possible.

Signed-off-by: David Lechner <david@pybricks.com>

tests/basics/python34.py

@@ -6,26 +6,23 @@ except NameError:
     print("SKIP")
     raise SystemExit
 
-# from basics/fun_kwvarargs.py
-# test evaluation order of arguments (in 3.4 it's backwards, 3.5 it's fixed)
-def f4(*vargs, **kwargs):
-    print(vargs, kwargs)
+
 def print_ret(x):
     print(x)
     return x
-f4(*print_ret(['a', 'b']), kw_arg=print_ret(None))
 
 # test evaluation order of dictionary key/value pair (in 3.4 it's backwards)
 {print_ret(1):print_ret(2)}
 
+
 # from basics/syntaxerror.py
 def test_syntax(code):
     try:
         exec(code)
     except SyntaxError:
         print("SyntaxError")
-test_syntax("f(*a, *b)") # can't have multiple * (in 3.5 we can)
-test_syntax("f(*a, b)") # can't have positional after *
+
+
 test_syntax("f(**a, b)") # can't have positional after **
 test_syntax("() = []") # can't assign to empty tuple (in 3.6 we can)
 test_syntax("del ()") # can't delete empty tuple (in 3.6 we can)