pcm_meter.c issue at s16_update

Hi,

It would be great to have a fix/patch from Pavel in the main codebase. I've tested his fix and it worked fine.

Just to remind what the issue is - while switching from one web radio station to another there is a high CPU usage for about 20 seconds. Because of that high CPU consumption almost all other processes are blocked. The fix from Pavel helps to avoid this situation.

Without the ALSA patch I need to make a custom ALSA build every time I release my software. This is very annoying.

Thanks in advance!