ltlsynt: extract In/Out AP processing in separate file

We'd like to reuse the --ins/--outs matching in ltlfilt
as well, so let's put that code in a common file.

* bin/common_ioap.cc, bin/common_ioap.hh: New files.
* bin/ltlsynt.cc: Extracted from here.
* bin/Makefile.am: Add them.

bin/common_ioap.hh

@@ -0,0 +1,51 @@
+// -*- coding: utf-8 -*-
+// Copyright (C) by the Spot authors, see the AUTHORS file for details.
+//
+// This file is part of Spot, a model checking library.
+//
+// Spot is free software; you can redistribute it and/or modify it
+// under the terms of the GNU General Public License as published by
+// the Free Software Foundation; either version 3 of the License, or
+// (at your option) any later version.
+//
+// Spot is distributed in the hope that it will be useful, but WITHOUT
+// ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+// or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public
+// License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+#pragma once
+
+#include "common_sys.hh"
+#include <optional>
+#include <regex>
+#include <string>
+#include <vector>
+#include <unordered_map>
+#include <spot/tl/formula.hh>
+
+// --ins and --outs, as supplied on the command-line
+extern std::optional<std::vector<std::string>> all_output_aps;
+extern std::optional<std::vector<std::string>> all_input_aps;
+
+// Comma-separated list of strings, such as those passed to --ins/--outs
+void split_aps(const std::string& arg, std::vector<std::string>& where);
+
+// process the all_output_aps and all_input_aps above to
+// fill regex_in, regex_out, and identifier_map.
+void process_io_options();
+
+// Store refirst, separate the filters that are regular expressions from
+// the others.  Compile the regular expressions while we are at it.
+extern std::vector<std::regex> regex_in;
+extern std::vector<std::regex> regex_out;
+// map identifier to input/output (false=input, true=output)
+extern std::unordered_map<std::string, bool> identifier_map;
+
+// Separate the set of the atomic propositions appearing in f, into
+// two vectors: input APs and output APs, becased on regex_in,
+// regex_out, and identifier_map.
+std::pair<std::vector<std::string>, std::vector<std::string>>
+filter_list_of_aps(spot::formula f, const char* filename, int linenum);