add API (tos_task_create_dyn & tos_task_walkthru & tos_task_curr_task_get)

tos_task_create_dyn: create task with dynamic allocated task handler and stack
tos_task_walkthru: API to walk through the statistic list of all the existing task
tos_task_curr_task_get: get current running task handler

kernel/core/tos_global.c

@@ -36,6 +36,12 @@ k_tick_t            k_cpu_tick_per_second       = TOS_CFG_CPU_TICK_PER_SECOND;
 
 k_cycle_t           k_cpu_cycle_per_tick        = (k_cycle_t)0u;
 
+#if TOS_CFG_TASK_DYNAMIC_CREATE_EN > 0u
+TOS_LIST_DEFINE(k_dead_task_list);
+#endif
+
+TOS_LIST_DEFINE(k_stat_list);
+
 TOS_LIST_DEFINE(k_tick_list);
 
 #if TOS_CFG_FAULT_BACKTRACE_EN > 0u