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.