done. UART tx (9600bps), clock select system(init_custom.c), fix bug of searchpath

1. add board_spec.h to handle different board development

2. config.bat:
include path of "-I ./" fail on root path
add script to change above to "-I ."

3. delay.h:
use CPU_Speed_Mhz as delay parameter (defined in board_spec.h)