Discard MSC_SCAN events

Given that only EV_KEY events are being mapped, without their scancode
counterparts, we just drop all scancode events to avoid having to map
them too, to syncing it with the corresponding mapped keys. This is
expected to be harmless.

caps2esc.c

@@ -39,6 +39,9 @@ int main(void) {
     setbuf(stdin, NULL), setbuf(stdout, NULL);
 
     while (read_event(&input)) {
+        if (input.type == EV_MSC && input.code == MSC_SCAN)
+            continue;
+
         if (input.type != EV_KEY) {
             write_event(&input);
             continue;