various bugfixes

various bugfixes

- don't parse -X option because such an option doesn't exist
- allow argument for --sleep-min option
- fix handling of .voc magic string
- fix handling of .voc files on big-endian machines
- remove superfluous "size" parameter from check_wavefile_space macro
- reallocate buffer only if needed in check_wavefile_space
- fix playback of >2GB .wav files
- skip over padding bytes in .wav files
- fix memory leak when playing .voc silence blocks
- fix file length when recording >2GB .wav files
- fix recording of >4GB files