better error message when no audio devies found
WIP: tidying up AudioDevice.cpp
add NoAudioDevice class

compiles, but doesn't work
added noAudioDevice thread

compiles, but untested
removed unused preprocessor define
compiles, but doesn't link
WIP: runs, but crashes with --nodevice option
bugfix for AUDIO_DEVICE index checks
add SINGLETON to NoAudioDevice
dummy audio device works, sortof

basic scheme evals work, but more compilcated ones throw a "maximum
runtime exceeded" error
fix overflow bug in sleep duration for dummy audio device
better error messages for dsp:set! in nodevice mode
Merge branch 'master' into nodevice-audio

* master:
  add libghttp example
  libghttp updates
noaudio branch compiles on Linux
significant improvements to ghttp.xtm (lib and example)
update ghttp.xtm test
remove some (unused) library loading guff from scheme.xtm
fix banner formatting for ARCH, CPU, ATRRS
refactor AudioDevice/NoAudioDevice inheritance stuff

not sure if this is 100% right, needs more testing.
Merge branch 'master' into nodevice-audio

* master:
  renanes for jansson lib
  emacs: update eldoc to show better (and colored) type and arg lists
  add 'quiet flag to initial load call for std.xtm
  remove reference to definec in DSP callback message
  refactor precomp stuff
  add 'quiet flag to precomp lib load calls
  add quiet option to sys:load
  more emacs-mode font-locking bugfixes
  update ghttp.xtm test
  significant improvements to ghttp.xtm (lib and example)

Conflicts:
	include/AudioDevice.h
	libs/external/ghttp.xtm