1. This is just a temporary solution, it will be removed when umm_malloc is ready
2. Support memory canaries mechanism
2. Add debug code to show allocated memory info
The thread-local-storage feature in FreeRTOS attaches an application-usable array of pointers to a thread control block. These pointers usually point to a structure the thread allocates. When a thread gets (voluntarily or involuntarily) destroyed, this memory can leak. This merge adds a matching second array of user-settable pointers to destructor routines. As soon as the task gets cleaned up (which happens in the idle thread), the destructors get called and the memory can be freed.
See merge request !19
rtos: change XT_CLOCK_FREQ from 13MHz to 80MHz
Freq has been change to `80MHz` in system_init, otherwise system tick will not be accurate now.
Maybe we can config freq by menuconfig.
See merge request !8
