[BSP] fix UART3 issue in STM32F40x.
[bsp] Fix serial 3 issue in beaglebone.
[libcpu] fix spell wrong.
[building] fix command too long issue under win32.
[Kernel] fix spell wrong in comments.
[pthreads] fix pthread_cond_init issue when attr is NULL.
[newlib] Remove compiling warning.
[DFS] fix copy command issue.
Merge pull request #309 from BernardXiong/stable-v1.2.x

prepare RT-Thread 1.2.2 release