Add play-waveform and play-sine to openal.examples
rosetta-code.metronome: use openAL to play sound

This brings cross-platform compatibility
rosetta-code.metronome: remove useless close-window call
rosetta-code.metronome: simplify stack shuffling
rosetta-code.metronome: correct disposal of timer
rosetta-code.metronome: add example as MAIN:
rosetta-code.metronome: fix metronome to stop the timer.
combinators.extras: adding 4bi* and 4bi@.
math.combinatorics: adding all-combinations? and all-permutations?.
colors: more generic methods, simpler api.
colors.cmyk: fix docs.