Add retry to icom_get_ptt

https://github.com/Hamlib/Hamlib/issues/1283

rigs/icom/icom.c

@@ -5068,10 +5068,14 @@ int icom_get_ptt(RIG *rig, vfo_t vfo, ptt_t *ptt)
 {
     unsigned char pttbuf[MAXFRAMELEN];
     int ptt_len, retval;
+    int retry=5;
 
     ENTERFUNC;
-    retval = icom_transaction(rig, C_CTL_PTT, S_PTT, NULL, 0,
+
+    do {
+        retval = icom_transaction(rig, C_CTL_PTT, S_PTT, NULL, 0,
                               pttbuf, &ptt_len);
+    } while(--retry >0 && retval != RIG_OK);
 
     if (retval != RIG_OK)
     {

rigs/icom/icom.h

@@ -35,7 +35,7 @@
 #include <sys/time.h>
 #endif
 
-#define BACKEND_VER "20230426"
+#define BACKEND_VER "20230503"
 
 #define ICOM_IS_ID31 rig_is_model(rig, RIG_MODEL_ID31)
 #define ICOM_IS_ID51 rig_is_model(rig, RIG_MODEL_ID51)