Hard latency restriction for the PulseAudio backend.

[szlop]

The changes add two optional arguments to the player and recorder functions:

• maxlatencyis translated to the PulseAudiobufattr.maxlength`` parameter, which sets a limit for the internal audio buffer and such restricts latency.
• report_under_overflow is an optional boolean debug argument, which enables the reporting of buffer underflows and overflows to the terminal.

The changes are meant for use-cases, which prioritize a defined latency over interruption-free playback/recording.