1. Added to the export table in export_test.py.
2. Added to the build table in build_release.py
3. Added the compilation directives to RTX os files.
Notice:
It would be better to change WORDS_STACK_SIZE definition in libraries/rtos/rtx/cmsis_os.h
from 512 to 128 for LPC11U35 and LPC1114 micros compiled by GCC toolchain with newlib-nano,
but I don't know the good way at this moment.
The INITIAL_SP value used by RTX was originally at the 4k limit instead
of at the 8k limit. The HEAP_START macro was defined to __HeapLimit
but the heap really starts at __end__. __HeapLimit is just used for
some link time sanity checks to verify that the heap and stack can
grow a bit without colliding.