Ported Facebook "Defragmentation" feature.

** Timer support
https://github.com/facebook/mysql-5.6/commit/c75a413edeb96eb99bf11d7269bdfea06f96d6b6

** Defragmentation feature
https://github.com/facebook/mysql-5.6/commit/a2d3a747426735c3a5f5feca8af8607f8acdc5a6
https://github.com/facebook/mysql-5.6/commit/def96c83fead34107d4122ec77364010d0edfa00
https://github.com/facebook/mysql-5.6/commit/9c67c5db5de056672df27e0cc995af652ad353da
https://github.com/facebook/mysql-5.6/commit/921a81b707673bc5bec324e17eb597b12e2232a6
https://github.com/facebook/mysql-5.6/commit/aa519bd44c16d8081d1ace194b383c1983794dd7
https://github.com/facebook/mysql-5.6/commit/fea7d13ca457ea7bbb38a2b36ae418c57c110139
https://github.com/facebook/mysql-5.6/commit/09b29d305cf380ecb241f163e1fbd68749688572
https://github.com/facebook/mysql-5.6/commit/9284abb38d6f968582dbd83a67d137ce7a7bd9c7
https://github.com/facebook/mysql-5.6/commit/dbd623df3a6b25fd8eb0216d469444d111e1de3c
https://github.com/facebook/mysql-5.6/commit/aed55dc4385d0a7c92eaca4d8db2f12c916dc4ab
https://github.com/facebook/mysql-5.6/commit/aad5c82ff8a5d40c84df5018365230da90e892a8

** And changed some code for gcc/g++ 4.4 and default value of some system variables.