local: make local_kind function accessible

The kind-definitions are contained in the header file:
  LOCAL_FLUSH 0
  LOCAL_ADD 1
  LOCAL_CHANGE 2

The function (local_kind) that converts them into strings again
is private. New addons (for example openwrt ubus bindings) that make
use of babeld should also use the same function to convert the kind
to string format. This allows to ensure uniformity over all addons.
Signed-off-by: Nick Hainke <vincent@systemli.org>

local.c

@@ -80,7 +80,7 @@ write_timeout(int fd, const void *buf, int len)
     }
 }
 
-static const char *
+const char *
 local_kind(int kind)
 {
     switch(kind) {

local.h

@@ -55,3 +55,4 @@ int local_read(struct local_socket *s);
 int local_header(struct local_socket *s);
 struct local_socket *local_socket_create(int fd);
 void local_socket_destroy(int i);
+const char *local_kind(int kind);