SMP emulation. New implementation uses dynamic CPU quantum value and takes
full advantage of the trace cache. Each emulated processor will execute
the whole trace before switching to the next processor.
* It is also safe to use large (up to 16 instructions) quantum values for
the SMP emulation now and improve performance even further.
The same merge also completely fixes SF bug :
[3312237] stepN command might be not working properly
Handlers chaining speedups are also supported with SMP emulation now.