highest SNR event within each buffer, but implement proper per-channel
threshold crossing detection with state preserved across buffers.

- update for change of "channel" tag to "channel-name"
- don't combine trigger streams, write each to a separate output file
  (temporarily, to work around a segfault in n-to-1)

optional.  This helps make the whitener useful outside of GW data
processing.

into tags

- reduce operation count in chisquared() function
- various tweaks trying to track down sources of poor behaviuor

- reduce operation count in chisquared() function