isisd: API: basic area config

Move out basic area configuration (metric type, overload and attachment
bits, dynamic hostname extension enable) into isis_vty.c.

[v2: moved stuff back here that accidentally was in the previous patch]

Signed-off-by: David Lamparter <equinox@opensourcerouting.org>
diff --git a/isisd/isisd.h b/isisd/isisd.h
index 2803a64..691d134 100644
--- a/isisd/isisd.h
+++ b/isisd/isisd.h
@@ -141,6 +141,12 @@
 int isis_area_get (struct vty *vty, const char *area_tag);
 void print_debug(struct vty *, int, int);
 
+void isis_area_overload_bit_set(struct isis_area *area, bool overload_bit);
+void isis_area_attached_bit_set(struct isis_area *area, bool attached_bit);
+void isis_area_dynhostname_set(struct isis_area *area, bool dynhostname);
+void isis_area_metricstyle_set(struct isis_area *area, bool old_metric,
+			       bool new_metric);
+
 void isis_vty_init (void);
 
 /* Master of threads. */