Add AArch64 support to strace

AArch64 has been included in linux from 3.7 onwards.
Add support for AArch64 in strace, tested on linux in a simulator.

* configure.ac: Support AArch64.
* defs.h [AARCH64]: Include <sys/ptrace.h>, define TCB_WAITEXECVE.
* ipc.c (indirect_ipccall): Support AArch64.
* process.c (struct_user_offsets): Likewise.
* syscall.c [AARCH64]: Include <asm/ptrace.h>,  <sys/uio.h>, and
<elf.h>.  Define struct user_pt_regs regs.
(get_scno, get_syscall_result): Support AArch64 using PTRACE_GETREGSET.
(get_syscall_args, get_error): Support AArch64.
* linux/aarch64/ioctlent.h.in: New file.
* linux/aarch64/syscallent.h: New file, based on linux 3.7 version of
asm-generic/unistd.h.

Signed-off-by: Steve McIntyre <steve.mcintyre@linaro.org>
diff --git a/configure.ac b/configure.ac
index a9f8d15..f44eaf1 100644
--- a/configure.ac
+++ b/configure.ac
@@ -56,6 +56,10 @@
 	arch=arm
 	AC_DEFINE([ARM], 1, [Define for the ARM architecture.])
 	;;
+aarch64*)
+	arch=aarch64
+	AC_DEFINE([AARCH64], 1, [Define for the AArch64 architecture.])
+	;;
 avr32*)
 	arch=avr32
 	AC_DEFINE([AVR32], 1, [Define for the AVR32 architecture.])