Supplement base/log.h with raw output function

This patch introduces the Genode::raw function that prints output
directly via a low-level kernel mechanism, if available.

On base-linux, it replaces the former 'raw_write_str' function.
On base-hw, it replaces the former kernel/log.h interface.

Fixes #2012

repos/base/src/lib/base/log.cc

@@ -42,3 +42,20 @@ void Log::_release()
 	_lock.unlock();
 }
 
+
+void Raw::_acquire()
+{
+	/*
+	 * Mark raw output with distinct color
+	 */
+	_output().out_string("\033[32mKernel: ");
+}
+
+
+void Raw::_release()
+{
+	/*
+	 * Reset color and add newline
+	 */
+	_output().out_string("\033[0m\n");
+}

repos/base/src/lib/base/raw_output.cc

@@ -0,0 +1,35 @@
+/*
+ * \brief  Access to raw output back end
+ * \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.
+ */
+
+/* Genode includes */
+#include <base/log.h>
+
+/* base-internal includes */
+#include <base/internal/unmanaged_singleton.h>
+#include <base/internal/output.h>
+#include <base/internal/raw_write_string.h>
+
+using namespace Genode;
+
+
+Output &Raw::_output()
+{
+	struct Write_fn { void operator () (char const *s) { raw_write_string(s); } };
+
+	typedef Buffered_output<256, Write_fn> Buffered_raw_output;
+
+	static Buffered_raw_output *buffered_raw_output =
+		unmanaged_singleton<Buffered_raw_output>(Write_fn());
+
+	return *buffered_raw_output;
+}

repos/base/src/lib/ldso/symbol.map

@@ -36,7 +36,6 @@
 		wait_for_continue;
 		stdout_write;
 		stdout_reconnect;
-		raw_write_str;
 
 		/* Testing */
 		extern "C++" {