Update README.md

Update rtdef.h

[Tools] Fix the buildlib with LOCAL_* options group

[tools] Add better way to generate MDK project file.

[Kernel] Change the version number to v2.0.1.

Merge pull request RT-Thread#425 from BernardXiong/master

[DeviceDrivers] Add more sensor drivers.

Prepare for RT-Thread 1.2.4 release.

Merge pull request RT-Thread#370 from grissiom/romfs-next

romfs: fix a use-before-set bug on checking the dirent

[LIBC] fix the open mode when using fopen in arm libc.

RT-Thread v2.0.0 beta