lib/index: Implement new indexer

Implement a new message indexer consisting of a single-threaded scanner
and a multi-threaded indexer.

This allows for a number of optimizations as well as background
indexing, though this initial version should be behave similar to the
old indexer.

lib/index/test-scanner.cc

@@ -0,0 +1,68 @@
+/*
+** Copyright (C) 2017 Dirk-Jan C. Binnema <djcb@djcbsoftware.nl>
+**
+**  This library is free software; you can redistribute it and/or
+**  modify it under the terms of the GNU Lesser General Public License
+**  as published by the Free Software Foundation; either version 2.1
+**  of the License, or (at your option) any later version.
+**
+**  This library 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
+**  Lesser General Public License for more details.
+**
+**  You should have received a copy of the GNU Lesser General Public
+**  License along with this library; if not, write to the Free
+**  Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA
+**  02110-1301, USA.
+*/
+
+#include <vector>
+#include <glib.h>
+
+#include <iostream>
+#include <sstream>
+
+#include "mu-scanner.hh"
+#include "mu-utils.hh"
+
+using namespace Mu;
+
+
+static void
+test_scan_maildir ()
+{
+	allow_warnings();
+
+	Scanner scanner{"/home/djcb/Maildir",
+                [](const dirent* dentry)->bool {
+                        g_print ("%02x %s\n", dentry->d_type, dentry->d_name);
+                        return true;
+                },
+                [](const std::string& fullpath, const struct stat* statbuf,
+                   auto&& info)->bool {
+                        g_print ("%s %zu\n", fullpath.c_str(), statbuf->st_size);
+                        return true;
+                }
+        };
+	g_assert_true (scanner.start());
+
+        while (scanner.is_running()) {
+                sleep(1);
+        }
+}
+
+int
+main (int argc, char *argv[]) try
+{
+	g_test_init (&argc, &argv, NULL);
+
+	g_test_add_func ("/utils/scanner/scan-maildir", test_scan_maildir);
+
+	return g_test_run ();
+
+
+} catch (const std::runtime_error& re) {
+	std::cerr << re.what() << "\n";
+	return 1;
+}