GSdx-ogl linux:
+ Change pthread with std::thread
+ Remove semaphores for linux, they are not used, and anyway, if we want portability
	we should reimplement it with std::thread mutexe

One pthread function who escaped...(however it should not have done any harm)

+ Remove old code(#if 0 & #endif are gone)
+ Use space for indentation

Remove a forgotten unused variable