Added some x86_64 system/kernel headers and kernel Jamfiles.

* Not all of these headers are correct yet, just adding what's necessary
  to get things to compile for the time being.

headers/private/system/arch/x86_64/arch_commpage_defs.h

@@ -0,0 +1,15 @@
+/*
+ * Copyright 2012, Alex Smith, [email protected].
+ * Distributed under the terms of the MIT License.
+ */
+#ifndef _SYSTEM_ARCH_x86_64_COMMPAGE_DEFS_H
+#define _SYSTEM_ARCH_x86_64_COMMPAGE_DEFS_H
+
+#ifndef _SYSTEM_COMMPAGE_DEFS_H
+#	error Must not be included directly. Include <commpage_defs.h> instead!
+#endif
+
+// FIXME: correct address
+#define ARCH_USER_COMMPAGE_ADDR (0xffff0000)
+
+#endif	/* _SYSTEM_ARCH_x86_64_COMMPAGE_DEFS_H */

headers/private/system/arch/x86_64/arch_real_time_data.h

@@ -0,0 +1,17 @@
+/*
+ * Copyright 2006, Ingo Weinhold <[email protected]>.
+ * All rights reserved. Distributed under the terms of the MIT License.
+ */
+#ifndef _KERNEL_ARCH_REAL_TIME_DATA_H
+#define _KERNEL_ARCH_REAL_TIME_DATA_H
+
+#include <StorageDefs.h>
+#include <SupportDefs.h>
+
+
+struct arch_real_time_data {
+	bigtime_t	system_time_offset;
+	uint32		system_time_conversion_factor;
+};
+
+#endif	/* _KERNEL_ARCH_REAL_TIME_DATA_H */