JIT compile anonymous functions * jit-ir.h (jit_block::front, jit_block::back): New function. (jit_call::jit_call): New overloads. (jit_return): New class. * jit-typeinfo.cc (octave_jit_create_undef): New function. (jit_operation::to_idx): Correctly handle empty type vector. (jit_typeinfo::jit_typeinfo): Add destroy_fn and initialize create_undef. * jit-typeinfo.h (jit_typeinfo::get_any_ptr, jit_typeinfo::destroy, jit_typeinfo::create_undef): New function. * pt-jit.cc (jit_convert::jit_convert): Add overload and refactor. (jit_convert::initialize, jit_convert_llvm::convert_loop, jit_convert_llvm::convert_function, tree_jit::do_execute, jit_function_info::jit_function_info, jit_function_info::execute, jit_function_info::match): New function. (jit_convert::get_variable): Support function variable lookup. (jit_convert_llvm::convert): Handle loop/function agnostic stuff. (jit_convert_llvm::visit): Handle function creation as well. (tree_jit::execute): Move implementation to tree_jit::do_execute. (jit_info::compile): Call convert_loop instead of convert. * pt-jit.h (jit_convert::jit_convert): New overload. (jit_convert::initialize, jit_convert_llvm::convert_loop, jit_convert_llvm::convert_function, tree_jit::do_execute): New function. (jit_convert::create_variable, jit_convert_llvm::initialize): Update signature. (tree_jit::execute): Made static. (tree_jit::tree_jit): Made private. (jit_function_info): New class. * ov-usr-fcn.cc (octave_user_function::~octave_user_function): Delete jit_info. (octave_user_function::octave_user_function): Maybe JIT and use is_special_expr and special_expr. (octave_user_function::special_expr): New function. * ov-usr-fcn.h (octave_user_function::is_special_expr, octave_user_function::special_expr, octave_user_function::get_info, octave_user_function::stash_info): New function. * pt-decl.h (tree_decl_elt::name): New function. * pt-eval.cc (tree_evaluator::visit_simple_for_command, tree_evaluator::visit_while_command): Use static tree_jit methods.