This commit adds a waveform audio previewer.

	+ previewers: Adds an audio previewer.
	+ elements: Add this previewer as a child of audio elements.
	+ Adds a new folder "coptimizations"
	+ Adds a new C extension, renderer, which renders the
	  samples on a cairo surface.
	+ Makefile.am:
	+ /* Fallthrough */
	+ configure.ac:
	+ autogen.sh:
	+ Updates to compile the renderer.
previewers: implements a pipelineCPUAdapter class.

	+ And use it in waveforms.