Add Device Electronic Signature support.

Working unique id support, but not 100% convinced that this is the "least surprise"
path.  ST's docs provide the bits from low to high, in 2xu16 and 2xu32.
But to get it back as a "u96" the highest bits should be first?

lib/stm32/f1/Makefile

@@ -31,7 +31,7 @@ ARFLAGS		= rcs
 OBJS		= vector.o rcc.o gpio.o usart.o adc.o spi.o flash.o nvic.o \
 		  rtc.o i2c.o dma.o systick.o exti.o scb.o ethernet.o \
 		  usb_f103.o usb.o usb_control.o usb_standard.o can.o \
-		  timer.o usb_f107.o
+		  timer.o usb_f107.o desig.o
 
 VPATH += ../../usb:../