Fix link option to msgpack
Insert atack.h in test to distribution file
Fix code style
Stop using -O4.

-O4 is undocumented in gcc, and ignored by intel compiler.
Remove unused m4 file.
Add -pthread.
add remove_session method to session_pool
Merge pull request #11 from gwtnb/stop-using-o4

Stop using -O4.
Merge pull request #14 from kmaehashi/remove-from-session-pool

add remove_session method to session_pool
Merge pull request #12 from gwtnb/pthread

Add -pthread.
Merge pull request #10 from jubatus/fix-makefile-for-test

Fix makefile for test