fix compiler warnings

ncd/NCDValue.c

@@ -700,4 +700,5 @@ int NCDValue_Compare (NCDValue *o, NCDValue *v)
     }
     
     ASSERT(0)
+    return 0;
 }

ncd/modules/net_backend_wpa_supplicant.c

@@ -343,7 +343,7 @@ void process_pipe_handler_send (struct instance *o, uint8_t *data, int data_len)
     // prefix, so don't fail if there isn't one.
     size_t l1;
     size_t l2;
-    if ((l1 = data_begins_with(data, data_len, o->ifname)) && (l2 = data_begins_with(data + l1, data_len - l1, ": "))) {
+    if ((l1 = data_begins_with((char *)data, data_len, o->ifname)) && (l2 = data_begins_with((char *)data + l1, data_len - l1, ": "))) {
         data += l1 + l2;
         data_len -= l1 + l2;
     }