[DISCO/NUCLEO_L053xx] adding to RTOS - part2

Stack sizes has to be reduced because of the limited 8K RAM.
[DISCO_L053xx] wrong STDIO UART

Correction of a wrong stdio uart - some tests failed because of this.
[DISCO_L053xx] RTC LSE/LSI problem

The mcu STM32L053C8 seems to have a problem in the RCC - LSE hardware
block. The Disco_L053 don't have a 32kHz crystal connected to LSE port
pins in contrast to NUCLEO_L053.
During initialization the HAL tests if it can start the LSE oscillator.
The Flag LSERDY in RCC_CSR is set to 1 by RCC clock control when the
oscillator runs stable. Without a crystal the flag shouldn't be set and
the HAL trys to start the internal LSI oscillator.
But the flag is always set to 1 also without a crystal. That's why the
RTC doesn't start.
[DISCO_L053xx] exporter to µVision