Don't include arch.h, include sysdep.h instead

arch.h is supposed to be a simple configuration file and few have inclusion
guards.  sysdep.h is the proper interface to use.
diff --git a/fetch.c b/fetch.c
index bce949f..a1eb8f4 100644
--- a/fetch.c
+++ b/fetch.c
@@ -22,8 +22,8 @@
 #include <string.h>
 
 #include "fetch.h"
+#include "sysdep.h"
 #include "value.h"
-#include "arch.h"
 #include "type.h"
 
 #ifdef ARCH_HAVE_FETCH_ARG
diff --git a/lens_enum.c b/lens_enum.c
index 1af94d2..52edd73 100644
--- a/lens_enum.c
+++ b/lens_enum.c
@@ -1,6 +1,6 @@
 /*
  * This file is part of ltrace.
- * Copyright (C) 2011 Petr Machata, Red Hat Inc.
+ * Copyright (C) 2011, 2012 Petr Machata, Red Hat Inc.
  *
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public License as
@@ -22,10 +22,10 @@
 #include <assert.h>
 #include <string.h>
 
-#include "arch.h"
 #include "lens_enum.h"
 #include "lens_default.h"
 #include "value.h"
+#include "sysdep.h"
 #include "type.h"
 
 struct enum_entry {
diff --git a/sysdeps/linux-gnu/breakpoint.c b/sysdeps/linux-gnu/breakpoint.c
index 40a8436..fe336b1 100644
--- a/sysdeps/linux-gnu/breakpoint.c
+++ b/sysdeps/linux-gnu/breakpoint.c
@@ -29,7 +29,6 @@
 
 #include "common.h"
 #include "backend.h"
-#include "arch.h"
 #include "sysdep.h"
 #include "breakpoint.h"
 #include "proc.h"