Added new Endpoint_ClearStatusStage() convenience function to assist with the status stages of control transfers.
Removed vague USB_IsConnected global - test USB_DeviceState or USB_HostState explicitly to gain previous functionality.
Removed USB_IsSuspended global - test USB_DeviceState against DEVICE_STATE_Suspended instead.
Fixed possible enumeration errors from spinloops which may fail to exit if the USB connection is severed before the exit condition becomes true.
Change MIDI demos to use real MIDI command values, and shift for the USB wrapper, rather than shift for the MIDI bytes. This is a little confusing for the MIDI USB wrapper, but allows for the use of real standardized MIDI command values.