c++: wrong parse with functors [PR64679]

c++: wrong parse with functors [PR64679]

Consider

  struct F {
    F(int) {}
    F operator()(int) const { return *this; }
  };

and

  F(i)(0)(0);

where we're supposed to first call the constructor and then invoke
the operator() twice.  However, we parse this as an init-declarator:
"(i)" looks like a perfectly valid declarator, then we see an '(' and
think it must be an initializer, so we commit and we're toast.  My
fix is to look a little bit farther before deciding we've seen an
initializer.

This is only a half of c++/64679, the other part of the PR is unrelated:
there the problem is that we are calling pushdecl while parsing
tentatively (in cp_parser_parameter_declaration_list), which is bad.

	PR c++/64679

gcc/cp/ChangeLog:

	* parser.cc (cp_parser_init_declarator): Properly handle a series of
	operator() calls, they are not part of an init-declarator.

gcc/testsuite/ChangeLog:

	* g++.dg/parse/functor1.C: New test.