[boost] [fiber] with assembler

I've uploaded a new version of boost.fiber to boost vault. It provides assembler for x86 (32/64bit) - PowerPC and ARM are planed. Performance of the raw context-switch is 6-12 times faster than swapcontext(POSIX). Mutexes, condition- and event-variables suspend fibers waiting on those sync. primitives and can be shared by fiber running on different threads (schedulers).