Fix kenwood_get_rit to utilize the +/- sign

https://github.com/Hamlib/Hamlib/issues/342

rigs/kenwood/kenwood.c

@@ -1678,9 +1678,9 @@ int kenwood_get_rit(RIG *rig, vfo_t vfo, shortfreq_t *rit)
         return retval;
     }
 
-    memcpy(buf, &priv->info[18], 5);
+    memcpy(buf, &priv->info[17], 6);
 
-    buf[5] = '\0';
+    buf[6] = '\0';
     *rit = atoi(buf);
 
     return RIG_OK;

rigs/kenwood/kenwood.h

@@ -27,7 +27,7 @@
 #include <string.h>
 #include "token.h"
 
-#define BACKEND_VER "20200712"
+#define BACKEND_VER "20200714"
 
 #define EOM_KEN ';'
 #define EOM_TH '\r'