Clean up #define situation for SYSTEM_CORE_CLOCK, APB_CLOCK, USE_HSI/HSE

sysclk fixes and example project

SYSTEM_CORE_CLOCK went away in favor of FUNCONF_SYSTEM_CORE_CLOCK

APB_CLOCK is only used in the i2c_slave.h and ch32v003_SPI.h files
so the references there have been maintained.

Added _ to FUNCONF_UART_PRINTF_BAUD

fix uart printf baud

Implement better monitor commands for GDB

Remove CFLAGS switch for STDOUT_UART

Example how to use the pin-change interrupt to monitor a cap touch sensor with about 6 bits of accuracy.

GPIO_branchless 2.0: STstyle pin references

Major change for adding funconfig.

Fix PIO build for funconfig branch