Make icom echo check skip the 1st two bytes of the frame

Saw an instance where the 1st 0xfe was corrupted so this allows for that

rigs/icom/frame.c

@@ -259,7 +259,9 @@ collision_retry:
             RETURNFUNC(-RIG_EPROTO);
         }
 
-        if (memcmp(buf, sendbuf, frm_len) != 0)
+        // first 2 bytes of everyting are 0xfe so we won't test those
+        // this allows some corruptin of the 0xfe bytes which has been seen in the wild
+        if (memcmp(&buf[2], &sendbuf[2], frm_len-2) != 0)
         {
             /* Frames are different? */
             /* Problem on ci-v bus? */

rigs/icom/icom.h

@@ -35,7 +35,7 @@
 #include <sys/time.h>
 #endif
 
-#define BACKEND_VER "20230718"
+#define BACKEND_VER "20230724"
 
 #define ICOM_IS_ID31 rig_is_model(rig, RIG_MODEL_ID31)
 #define ICOM_IS_ID51 rig_is_model(rig, RIG_MODEL_ID51)