Try to organize include files alphabetically.
Introduce some input/output pasrameter checks.

When setting device strings or sample rate, check if the new settings
asre different from the old ones and do nothing if the settings haven't
changed. The reduces the number of 'i/o device errors' since we don't
try to re-open the same device.
Suspend DSP during reconfiguration.
Merge branch 'master' into fft_filter