Missing parentheses in dictionary unpacking

[Kodiologist]

>>> {**(0 or {})}
{}
>>> astor.to_source(ast.parse("{**(0 or {})}"))
'{**0 or {}}\n'
>>> {**0 or {}}
  File "<stdin>", line 1
    {**0 or {}}
         ^
SyntaxError: invalid syntax

Originally reported by @martibi at https://github.com/hylang/hy/issues/2156.

[Kodiologist]

Contrast:

>>> ast.unparse(ast.parse("{**(0 or {})}"))
'{**(0 or {})}'

so we can probably just do whatever Python does for this.