tos_mmheap_check: get the information of the heap(space that is free and used)
tos_mmheap_pool_check: get the information of a pool
TOS_CFG_MMHEAP_DEFAULT_POOL_EN: enable the default pool of the heap(if user not set this, a default of 1u is set). if you wanna disable the default pool, you should call tos_mmheap_pool_add to add your own pool of the heap before tos_mmheap_alloc is called.
see examples/event_driven_at_module and examples/event_driven_hello_world, demo project: TencentOS-tiny\board\TencentOS_tiny_EVB_MX\KEIL\event_driven_hello_world
fix a tick list add bug: if a lower priority task has the same tick_expires with a higher priority task in the tick list, the lower should be added behind the higher one.
