[Benchmarking] Added multithreaded benchmark.
[GCC 4.4] No more lambdas.
[GCC 4.6] Standard hardware concurrency always return 0.

What a blame!
[Benchmarking] Added some benchmarks to measure scalability.
[Code Style] Minor fixes.
[Code Clean] Dropped unused include.
[Benchmarking] Massive refactoring over logger benchmarks.

 - Initialization function has been decomposed into separate file.
 - Utilized some constants like message format and message itself.
[Benchmarking] Filter measurement.