move eval of anon fcn handles and built-in and mex functions to pt-eval.cc For consistency with the evaluation of user-defined functions and scripts, move the evaluation of anonymous function handles and built-in and mex functions to the tree_evaluator class in pt-eval.cc. * pt-eval.h, pt-eval.cc (tree_evaluator::evaluate_anon_fcn_handle, tree_evaluator::execute_builtin_function, tree_evaluator::execute_mex_function): New functions extracted from tree_anon_fcn_handle::evalueate, octave_builtin::execute and octave_mex_function::execute, respectively. * ov-builtin.cc (octave_builtin::execute): Forward to tree_evaluator::execute_builtin_function. * ov-mex-fcn.cc (octave_mex_function::execute): Forward to tree_evaluator::execute_mex_function. * pt-fcn-handle.cc (tree_anon_fcn_handle::evaluate): Forward to tree_evaluator::evaluate_anon_fcn_handle. * mex.cc: Move call_mex inside octave namespace. * mex-private.h: New file. * libinterp/corefcn/module.mk: Update.

To cite GNU Octave in publications use:

  John W. Eaton, David Bateman, Søren Hauberg, Rik Wehbring (2022).
  GNU Octave version 7.1.0 manual: a high-level interactive language for
  numerical computations.
  URL https://www.gnu.org/software/octave/doc/v7.1.0/

A BibTeX entry for LaTeX users is:

  @manual{,
    title     = {{GNU Octave} version 7.1.0 manual: a high-level interactive language for numerical computations},
    author    = {John W. Eaton and David Bateman and S{\o}ren Hauberg and Rik Wehbring},
    year      = {2022},
    url       = {https://www.gnu.org/software/octave/doc/v7.1.0/},
  }

We have invested a lot of time and effort in creating GNU Octave, please
cite it when using it.  See also 'citation pkgname' for citing Octave
packages.