update deCAPTCHA

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定义 BOOST_SP_DISABLE_THREADS 使用非原子操作的 shared_ptr , 减少引用计数的开销.
at least gcc 4.4 is now the required compiler!

we can safely use what c++11 feature provided by gcc 4.4, gcc 4.4 is also what centos6 provided default compiler
travis: apply fix for boost with gcc 4.6.3
now comes the real fix for the mail sender!
decltype is not supported by gcc 4.4.7
很重要的一次修正

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update sqlite to 3.8
Revert "定义 BOOST_SP_DISABLE_THREADS 使用非原子操作的 shared_ptr , 减少引用计数的开销."

This reverts commit bad9cd466b9985e27f09e34a76f26ff5180cec62.

在 gcc 4.4.7 的 centos vps 上测试，观察到了 shared_ptr
因为线程不安全导致的问题。
code style

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