tests: c++: fix a C++03 conformance issue

tests: c++: fix a C++03 conformance issue

This fixes test 241 on xLC:

"input.y", line 42.11: 1540-0274 (S) The name lookup for "report" did not find a declaration.
"input.y", line 42.11: 1540-1292 (I) Static declarations are not considered for a function call if the function is not qualified.

where report is:

  static void
  report (std::ostream& yyo, int ival, float fval)
  {
    yyo << "ival: " << ival << ", fval: " <<  fval;
  }

and line 42 is:

  %printer { report (yyo, $$,       $<fval>$); } <ival>;

It turns out that indeed this function must not be declared static,
<http://stackoverflow.com/a/17662745/1353549>.  Let's put it into an
anonymous namespace.

Reported by Thomas Jahns.
http://lists.gnu.org/archive/html/bug-bison/2015-01/msg00059.html

* tests/actions.at (Qualified $$ in actions): Don't use "static",
prefer anonymous namespace.