Split button board into 2 16 button joysticks.

WPILib was unhappy with more than 16 buttons.

Change-Id: I3b874678d262245912f0f67896d8db6562fd8742
diff --git a/motors/usb/usb.cc b/motors/usb/usb.cc
index 7a6286e..e4a2b26 100644
--- a/motors/usb/usb.cc
+++ b/motors/usb/usb.cc
@@ -130,7 +130,7 @@
   device_descriptor_->AddUint16(product_id);  // idProduct
   // Increment this whenever you need Windows boxes to actually pay attention to
   // changes.
-  device_descriptor_->AddUint16(24);  // bcdDevice
+  device_descriptor_->AddUint16(25);  // bcdDevice
   // We might overwrite these string descriptor indices later if we get strings
   // to put there.
   device_descriptor_->AddByte(0);  // iManufacturer