cmdmon: add reserved fields to local command

Add two reserved fields initialized to zero to the new REQ_LOCAL3
command to allow adding more options (e.g. delay in activation) without
changing the command number again.

candm.h

@@ -239,6 +239,7 @@ typedef struct {
   Float distance;
   int32_t orphan;
   Float activate;
+  uint32_t reserved[2];
   int32_t EOR;
 } REQ_Local;