write gpsd.json when using gpsd_in

for each message with lat / lon received from gpsd, the message is
written as is to gpsd.json

net_io.c

@@ -3577,6 +3577,16 @@ static int handle_gpsd(struct client *c, char *p, int remote, int64_t now, struc
         fprintf(stderr, " gpsdebug: received from GPSD: \'%s\'\n", p);
     }
 
+    struct char_buffer msg;
+    char msg_buf[4096];
+    msg.alloc = 4096;
+    msg.buffer = msg_buf;
+    msg.len = 0;
+    if (strlen(p) < msg.alloc - 8) {
+        sprintf(msg.buffer, "%s\n", p);
+        msg.len = strlen(msg.buffer);
+    }
+
     // remove spaces in place
     char *d = p;
     char *s = p;
@@ -3659,6 +3669,9 @@ static int handle_gpsd(struct client *c, char *p, int remote, int64_t now, struc
 
     if (Modes.json_dir) {
         free(writeJsonToFile(Modes.json_dir, "receiver.json", generateReceiverJson()).buffer); // location changed
+        if (msg.len) {
+            writeJsonToFile(Modes.json_dir, "gpsd.json", msg);
+        }
     }
 
     return 0;