marsyas/basis.h: fix for c++11
marsyas: compile in c++11 mode
core: implement lockfree realvec-based queue
marsystems: improve AudioSink, AudioSource wrt reliability, latency

* Use lockfree queue to pass data between RtAudio thread and MarSystem
  thread.

* Do not busy-wait for fixed amount of time when queue full/empty.
  Instead, wait on a condition variable.

* Never wait in RtAudio thread if queue full/empty. Instead, return
  right away, writing silence in case of AudioSink. Only block
  MarSystem thread.

* Implement new "realtime" boolean control, which will minimize buffer to
  force smallest logically possible latency at the cost of tolerance to
  processing times of other parts of system.
cmake: add macro to enable c++11 for given target
cmake: marsyas: use 'target_enable_cpp11' macro
marsystems: AudioSource/Sink: suppress useless warnings
marsystems: AudioSource/Sink: state source of error on RtAudio error
documentation: add realvec_queue documentation
core: realvec_queue: fix indentation
core: realvec_queue: implement variable capacity
marsystems: AudioSink: support variable block size
marsystems: AudioSource: support variable block size
marsystems: AudioSource/Sink: clean up indentation
synchronize branch topic/realtime with master
<windows.h> is evil

Make sure "realvec_queue.h" is included before <windows.h> to avoid
conflict with min() and max() macros defined by the latter.
fix realvec_queue::write_capacity()
add framework for real-time execution of MarSystem and safe interaction
marsyasqt: new MarSystem wrapper
MarPlayer: use new Qt wrapper