detection sys.: correction and alternative

[ziyuan1135]

correction:

1. atomic_compare_exchange_strong(): cppreference與gcc的定義不一樣，須注意與修正。
   e.g. insert_watchpoint func. and find_watchpoint func. in src/core.c

alternative:

1. check_access func. 使用mutex，解決同時兩個processes都對同一個記憶體進行操作，且該記憶體位址並未註冊在watchpoints之case
   problem: lock會導致執行效率差
   trade offs: 照原本的，不要使用mutex，若發生上述case，ignore

2. watchpoints(array)位址存放方式: 使用slot與mod PAGE_SIZE(即offset)達到direct access，不須sequential search，即時間為big O(1)
   problem: 若collison高，則效果不好
   trade offs:照原本的，用sequential search即可

[Chih-En Lin]

1. atomic_compare_exchange_strong(): cppreference與gcc的定義不一樣，須注意與修正。

Actually, the C11 is the same as the GCC builtin __atomic function. It is different from compare and swap logic.
My fault.
Sorry.