utils: more flexible reading of /proc/sys/net

- changes nm_utils_get_proc_sys_net_value() to allow all values, not just 0,1
- adds nm_utils_get_proc_sys_net_value_with_bounds() for limiting valid values

src/NetworkManagerUtils.h

@@ -15,7 +15,7 @@
  * with this program; if not, write to the Free Software Foundation, Inc.,
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  *
- * Copyright (C) 2004 - 2010 Red Hat, Inc.
+ * Copyright (C) 2004 - 2011 Red Hat, Inc.
  * Copyright (C) 2005 - 2008 Novell, Inc.
  */
 
@@ -83,7 +83,13 @@ gboolean nm_utils_do_sysctl (const char *path, const char *value);
 
 gboolean nm_utils_get_proc_sys_net_value (const char *path,
                                           const char *iface,
-                                          guint32 *out_value);
+                                          gint32 *out_value);
+
+gboolean nm_utils_get_proc_sys_net_value_with_bounds (const char *path,
+                                                      const char *iface,
+                                                      gint32 *out_value,
+                                                      gint32 valid_min,
+                                                      gint32 valid_max);
 
 void nm_utils_complete_generic (NMConnection *connection,
                                 const char *ctype,