rt_ssize_t can give negative error code, which follows the unix style correctly

* Update thread-comm.md

* Update documentation/thread-comm/thread-comm.md
Co-authored-by: Man, Jianting (Meco) <920369182@qq.com>

* [rtdef] rename RT_WEAK attribute as rt_weak

* [rtdef] rename RT_USED attribute as rt_used

* [rtdef] rename RT_SECTION attribute as rt_section

* [rtdef] rename ALIGN attribute as rt_align

* [legacy] add RT_USED ALIGN RT_SECTION RT_WEAK as legacy support

append some information about menuconfig -s

* [document] Fix the doxygen file

* Overhaul of document, fixing multiple grammar mistakes and editing for clarity

* Further documentation grammar and spelling fixes

* Update English coding style for more idiomatic use

Fresh eyes on the English coding style guide.

Remove "speed bumps" to a native English reader to improve acceptance.

* Coding_style_en: fix plurality disagreement

将路径更新为IAR最新版本的路径

* updated adc.md

* fixed typo error

Co-authored-by: Njiangjianbo <jiangjianbo@rt-thread.com>

* [gcc][armcc][armclang] rtconfig.CROSS_TOOL->rtconfig.PLATFORM

* Fixed Program Memory Distribution-Basic.md

* removed errors

反应->反映

thead -> thread

Signed-off-by: NCathy Li <liyan@rt-thread.com>

Note that the word 'swtich' is wrong,
so that 'swtich' should been replaced with 'switch'.