* when playing back a sample from the sample cache, just take a pa_volume_t and not...

* when playing back a sample from the sample cache, just take a pa_volume_t and not a pa_cvolume_t as argument for the volume. Usually it is not known to the player of theses samples how many channels it has, hence it doesn't make any sense to allow him to pass a by-channel volume structure here.
* fix volume calculation when playing samples from the sample cache

git-svn-id: file:///home/lennart/svn/public/pulseaudio/trunk@784 fefdeb5f-60dc-0310-8127-8f9354f1896f