_Atomic support broken

[stevetremblett]

    Hmmmm, I tried, but the implementation is still incorrect, as `typedef _Atomic(_Bool) atomic_bool;` does not parse. This comes from e.g. LLVM `<stdatomic.h>`. I believe that is what my following code handled:

    # This is a bit ugly, but we need to process atomic specifier before qualifiers,
    # since _Atomic(int) has a conflict with _Atomic int.
    def p_declaration_specifiers_no_type_4(self, p):
        """ declaration_specifiers_no_type  : atomic_specifier declaration_specifiers_no_type_opt
        """
        p[0] = self._add_declaration_specifier(p[2], p[1], 'type')

Originally posted by @vit9696 in https://github.com/eliben/pycparser/issues/430#issuecomment-920053179

I am witnessing this error on the current release version.

[stevetremblett]

[eliben]

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