socket: Introduce API osmo_sockaddr_is_any

Change-Id: I2810a889fc14052d0e0be6a2b500ad4e5088ffa9
diff --git a/include/osmocom/core/socket.h b/include/osmocom/core/socket.h
index 79de6c5..06db5d0 100644
--- a/include/osmocom/core/socket.h
+++ b/include/osmocom/core/socket.h
@@ -31,6 +31,7 @@
 };
 
 int osmo_sockaddr_is_local(struct sockaddr *addr, unsigned int addrlen);
+int osmo_sockaddr_is_any(const struct osmo_sockaddr *addr);
 
 unsigned int osmo_sockaddr_to_str_and_uint(char *addr, unsigned int addr_len, uint16_t *port,
 					   const struct sockaddr *sa);