Add keyboard report debug print on V-USB.

vusb/vusb.c

@@ -42,6 +42,11 @@ void vusb_transfer_keyboard(void)
     if (usbInterruptIsReady()) {
         if (kbuf_head != kbuf_tail) {
             usbSetInterrupt((void *)&kbuf[kbuf_tail], sizeof(report_keyboard_t));
+            if (!debug_keyboard) {
+                print("keys: ");
+                for (int i = 0; i < REPORT_KEYS; i++) { phex(kbuf[kbuf_tail].keys[i]); print(" "); }
+                print(" mods: "); phex((kbuf[kbuf_tail]).mods); print("\n");
+            }
             kbuf_tail = (kbuf_tail + 1) % KBUF_SIZE;
         }
     }