Alter the ring buffer library headers to have both atomic and non-atomic...

Alter the ring buffer library headers to have both atomic and non-atomic insertion/removal routines. Modify the existing projects so that buffer operations performed in an ISR use the shorted non-atomic versions, as they are already performed in a blocking ISR.

Alter USBtoSerial demo so that it does not enter a blocking loop to send data from the USB to the USART, as this can cause dropped bytes in the reception code if large amounts of data are sent in both directions at the same time. Added a flush timer to the USBtoSerial code for the USART to USB interface, so that multiple bytes can be sent in the same USB packet.