Move timer from os to base repository

Since the timer and timeout handling is part of the base library (the
dynamic linker), it belongs to the base repository.

Besides moving the timer and its related infrastructure (alarm, timeout
libs, tests) to the base repository, this patch also moves the timer
from the 'drivers' subdirectory directly to 'src' and disamibuates the
timer's build locations for the various kernels. Otherwise the different
timer implementations could interfere with each other when using one
build directory with multiple kernels.

Note that this patch changes the include paths for the former os/timer,
os/alarm.h, os/duration.h, and os/timed_semaphore.h to base/.

Issue #3101

repos/base/include/timer_session/capability.h

@@ -0,0 +1,22 @@
+/*
+ * \brief  Timer session capability type
+ * \author Norman Feske
+ * \date   2008-08-16
+ */
+
+/*
+ * Copyright (C) 2008-2017 Genode Labs GmbH
+ *
+ * This file is part of the Genode OS framework, which is distributed
+ * under the terms of the GNU Affero General Public License version 3.
+ */
+
+#ifndef _INCLUDE__TIMER_SESSION__CAPABILITY_H_
+#define _INCLUDE__TIMER_SESSION__CAPABILITY_H_
+
+#include <base/capability.h>
+#include <timer_session/timer_session.h>
+
+namespace Timer { typedef Genode::Capability<Session> Session_capability; }
+
+#endif /* _INCLUDE__TIMER_SESSION__CAPABILITY_H_ */