migrate fully to meson build system

- drop old build system
- move shared include and source files to common directory
- drop "rc-" prefix from shared include and source files
- move executable-specific code to individual directories under src
- adjust top-level .gitignore file for new build system

This closes #489.

src/shared/wtmp.h

@@ -0,0 +1,26 @@
+/*
+ * rc-wtmp.h
+ * This is private to us and not for user consumption
+*/
+
+/*
+ * Copyright (c) 2017 The OpenRC Authors.
+ * See the Authors file at the top-level directory of this distribution and
+ * https://github.com/OpenRC/openrc/blob/HEAD/AUTHORS
+ *
+ * This file is part of OpenRC. It is subject to the license terms in
+ * the LICENSE file found in the top-level directory of this
+ * distribution and at https://github.com/OpenRC/openrc/blob/HEAD/LICENSE
+ * This file may not be copied, modified, propagated, or distributed
+ *    except according to the terms contained in the LICENSE file.
+ */
+
+#ifndef __RC_WTMP_H__
+#define __RC_WTMP_H__
+
+#include <utmp.h>
+
+void log_wtmp(const char *user, const char *id, pid_t pid, int type,
+		const char *line);
+
+#endif