Modified PostgreSQL's buffer manager from Clock Replacement Policy to Stack LRU
Main changes:
- Implemented the following functions in freelist-lru.c:
- StrategyUpdateAccessedBuffer
- StrategyShmemSize
- StrategyGetBuffer
- StrategyFreeBuffer
- Some test data to test the implementation against the original implementation by PostgreSQL
Changes to the original source codes are demarcated with modified by Anton Lee to help ease the search