Make fastsocket more friendly

The new features

1. Add direct TCP feature;
2. Add skb mem pool;
3. Add the RCS;
4. Support the SElinux. The old version will crashes when unload the fastsocket;
5. Add the socket mem pool;

Refactor the codes:

1. Split the fastsocket.c into fast_core.c and fast_api.c;
2. Eliminate the duplicated codes;
3. Eliminate the compile warnings of demo codes;
4. Add the test script

The bugs fixed:

1. Fix some typos in README.md
2. Fix the compile errors with the higher version gcc;
3. Fix one crash bug of demo codes;
4. Fix some potential memleaks;.