Keil RTX RTOS - tick-less example with LCD off.

This example is modification of rtx_tickless to demonstrate ultra low power consumption 
of Gecko processors in connection with RTX RTOS. Comparing to previous example it has LCD
turned off. There is also possible to disable part of RAM to lower power even further.
Low frequency crystal oscillator was disabled and low frequency RC oscillator used instead
to lower energy consumption even more.

project uses the Keil RTX RTOS, and gives a basic demonstration
of using two tasks; one sender generating number and one receiver.
The RTX is configured in tick-less mode, going into EM2 when
no tasks are active. This example is intended as a skeleton for new projects
using Keil RTX for energy aware applications.

Board:  Silicon Labs EFM32LG-STK3600
Device: EFM32LG990F256
