Let kenwood serial read remove non-printable chars from responses

Should help it be a bit more robust against bad serial data like this
https://github.com/Hamlib/Hamlib/issues/1652

rigs/kenwood/kenwood.c

@@ -231,6 +231,23 @@ struct confparams kenwood_cfg_params[] =
     { RIG_CONF_END, NULL, }
 };
 
+int remove_nonprint(char *s)
+{
+    int i, j = 0;
+    if (s == NULL) return 0;
+
+    for (i = 0; s[i] != '\0'; ++i)
+    {
+        if (isprint((unsigned char)s[i]))
+        {
+            s[j++] = s[i]; // Copy printable character
+        }
+    }
+    s[j] = '\0'; // Null-terminate the string
+
+    return j; // Return the new length of the string
+}
+
 
 /**
  * kenwood_transaction
@@ -424,6 +441,10 @@ transaction_read:
     rig_debug(RIG_DEBUG_TRACE, "%s: read_string len=%d '%s'\n", __func__,
               (int)strlen(buffer), buffer);
 
+    // this fixes the case when some corrupt data is returned
+    // let's us be a little more robust about funky serial data
+    remove_nonprint(buffer);
+
     if (retval < 0)
     {
         rig_debug(RIG_DEBUG_WARN,

rigs/kenwood/kenwood.h

@@ -28,7 +28,7 @@
 #include "token.h"
 #include "idx_builtin.h"
 
-#define BACKEND_VER "20241022"
+#define BACKEND_VER "20250107"
 
 #define EOM_KEN ';'
 #define EOM_TH '\r'