Pa_process: Fix output channel adaption by not skipping the conversion when the host and user number-of-channels are not equal.  Reported by Leif Asbrink when using an envy24 soundcard on Linux at it's native Int32 format with 1 or 2 channels.  Corresponding fix for input already in r1913.

git-svn-id: https://subversion.assembla.com/svn/portaudio/portaudio/trunk@1954 0f58301d-fd10-0410-b4af-bbb618454e57