alsa: Increase snprintf buffer size to fix warning (#566)

alsa: Increase snprintf buffer size to fix warning (#566)

Avoid compiler warning suggesting the buffer is too small:

../PortAudioLib/portaudio/src/hostapi/alsa/pa_linux_alsa.c: In function 'BuildDeviceList.constprop':
../PortAudioLib/portaudio/src/hostapi/alsa/pa_linux_alsa.c:1304:45: warning: '%s' directive output may be truncated writing up to 49 bytes into a region of size between 46 and 50 [-Wformat-truncation=]
             snprintf( buf, sizeof (buf), "%s%s,%d", hwPrefix, alsaCardName, devIdx );
                                             ^~                ~~~~~~~~~~~~
../PortAudioLib/portaudio/src/hostapi/alsa/pa_linux_alsa.c:1304:42: note: directive argument in the range [0, 2147483647]
             snprintf( buf, sizeof (buf), "%s%s,%d", hwPrefix, alsaCardName, devIdx );
                                          ^~~~~~~~~
../PortAudioLib/portaudio/src/hostapi/alsa/pa_linux_alsa.c:1304:13: note: 'snprintf' output between 3 and 65 bytes into a destination of size 50
             snprintf( buf, sizeof (buf), "%s%s,%d", hwPrefix, alsaCardName, devIdx );
             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~