Unification of native_capability.h

This patch establishes the sole use of generic headers across all
kernels. The common 'native_capability.h' is based on the version of
base-sel4. All traditional L4 kernels and Linux use the same
implementation of the capability-lifetime management. On base-hw, NOVA,
Fiasco.OC, and seL4, custom implementations (based on their original
mechanisms) are used, with the potential to unify them further in the
future.

This change achieves binary compatibility of dynamically linked programs
across all kernels.

Furthermore, the patch introduces a Native_capability::print method,
which allows the easy output of the kernel-specific capability
representation using the base/log.h API.

Issue #1993

repos/base-linux/src/lib/base/capability_raw.cc

@@ -0,0 +1,31 @@
+/*
+ * \brief  Capability
+ * \author Norman Feske
+ * \date   2016-06-16
+ */
+
+/*
+ * Copyright (C) 2016 Genode Labs GmbH
+ *
+ * This file is part of the Genode OS framework, which is distributed
+ * under the terms of the GNU General Public License version 2.
+ */
+
+#include <base/log.h>
+
+/* base-internal includes */
+#include <base/internal/capability_space_tpl.h>
+
+using namespace Genode;
+
+
+Native_capability::Raw Native_capability::raw() const
+{
+	/*
+	 * On Linux, we don't pass information as a 'raw' representation to
+	 * child components. So this function remains unused. We still need
+	 * to provide it to prevent link errors of noux, which relies on this
+	 * function for implementing 'fork' (not supported on base-linux).
+	 */
+	return { { 0, 0, 0, 0 } };
+}