AArch64: Add initial support for AArch64

This is the first patch out of a series of patches that add support for
AArch64, the new 64bit execution state of the ARMv8 Architecture. The
patches add support for LP64 programming model.

The patch adds:
* "arch-aarch64" to the architecture directories.
* "arch-aarch64/include" - headers used by libc
* "arch-aarch64/bionic":
    - crtbegin, crtend support;
    - aarch64 specific syscall stubs;
    - setjmp, clone, vfork assembly files.

Change-Id: If72b859f81928d03ad05d4ccfcb54c2f5dbf99a5
Signed-off-by: Serban Constantinescu <serban.constantinescu@arm.com>
diff --git a/libc/arch-aarch64/include/machine/exec.h b/libc/arch-aarch64/include/machine/exec.h
new file mode 100644
index 0000000..7437626
--- /dev/null
+++ b/libc/arch-aarch64/include/machine/exec.h
@@ -0,0 +1,50 @@
+/*	$OpenBSD: exec.h,v 1.9 2003/04/17 03:42:14 drahn Exp $	*/
+/*	$NetBSD: exec.h,v 1.6 1994/10/27 04:16:05 cgd Exp $	*/
+
+/*
+ * Copyright (c) 1993 Christopher G. Demetriou
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. The name of the author may not be used to endorse or promote products
+ *    derived from this software without specific prior written permission
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef _AARCH64_EXEC_H_
+#define _AARCH64_EXEC_H_
+
+#define	__LDPGSZ		4096
+
+#define	NATIVE_EXEC_ELF
+
+#define	ARCH_ELFSIZE		64
+
+#define	ELF_TARG_CLASS		ELFCLASS64		/* 64-bit objects */
+#define	ELF_TARG_DATA		ELFDATA2LSB
+#define	ELF_TARG_MACH		EM_AARCH64
+
+#define	_NLIST_DO_AOUT
+#define	_NLIST_DO_ELF
+
+#define	_KERN_DO_AOUT
+#define	_KERN_DO_ELF64
+
+#endif  /* _AARCH64_EXEC_H_ */