Add support for ARC Cores from Synopsys

Take #2 on mainlining strace support for ARC (last one was 4.6 based back
in March 2011), see
http://sourceforge.net/p/strace/mailman/message/27210168/

The syscall ABI is asm-generic/unistd.h based (so no legacy syscalls),
hence very similar to metag port.

test/* all seem to work well.

* linux/arc/ioctlent.h.in: New file.
* linux/arc/syscallent.h: Likewise.
* Makefile.am (EXTRA_DIST): Add linux/arc/ioctlent.h.in and
linux/arc/syscallent.h.
* configure.ac: Add ARC to the list of supported architectures.
* defs.h: Add ARC support.
* process.c (struct_user_offsets): Likewise.
* signal.c (sys_sigreturn): Likewise.
* syscall.c (print_pc, get_regset, get_regs, get_scno, get_syscall_args,
get_syscall_result, get_error): Likewise.
* util.c (change_syscall): Likewise.

Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
Acked-by: Mike Frysinger <vapier@gentoo.org>
diff --git a/process.c b/process.c
index e2fa25b..1a2181b 100644
--- a/process.c
+++ b/process.c
@@ -2513,6 +2513,8 @@
 	/* nothing */
 #elif defined(XTENSA)
 	/* nothing */
+#elif defined(ARC)
+	/* nothing */
 #endif
 	{ 0,			NULL					},
 };