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/Makefile.am b/Makefile.am
index 9d611f3..9187fa0 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -82,6 +82,8 @@
 	linux/alpha/ioctlent.h.in	\
 	linux/alpha/signalent.h		\
 	linux/alpha/syscallent.h	\
+	linux/arc/ioctlent.h.in		\
+	linux/arc/syscallent.h		\
 	linux/arm/ioctlent.h.in		\
 	linux/arm/syscallent.h		\
 	linux/avr32/ioctlent.h.in	\