lib: hide internal prefix list structures

These are about to be touched and there's no point in other code
touching into prefix list's internas.  Add some isolation.

Signed-off-by: David Lamparter <equinox@opensourcerouting.org>
diff --git a/lib/plist.c b/lib/plist.c
index 6107556..bdc31e8 100644
--- a/lib/plist.c
+++ b/lib/plist.c
@@ -30,25 +30,7 @@
 #include "stream.h"
 #include "log.h"
 
-/* Each prefix-list's entry. */
-struct prefix_list_entry
-{
-  int seq;
-
-  int le;
-  int ge;
-
-  enum prefix_list_type type;
-
-  int any;
-  struct prefix prefix;
-
-  unsigned long refcnt;
-  unsigned long hitcnt;
-
-  struct prefix_list_entry *next;
-  struct prefix_list_entry *prev;
-};
+#include "plist_int.h"
 
 /* List of struct prefix_list. */
 struct prefix_list_list
@@ -125,6 +107,11 @@
   return NULL;
 }
 
+const char *prefix_list_name (struct prefix_list *plist)
+{
+  return plist->name;
+}
+
 /* Lookup prefix_list from list of prefix_list by name. */
 struct prefix_list *
 prefix_list_lookup (afi_t afi, const char *name)