Fixes the zigzag for sizes 8 and 16

Previous data was using the "reverse ordering", assuming that we were using
the lookup for the load when converting from raster to zigzag
Adds required declarations for using bands
Replaces zig-zag with bands to makes it easier to mix scalar and pvq

This does not change the SNR and has very small effect on the rate.
Double-precision PVQ quantizer for upcoming experiments
Skip logging_test when logging isn't enabled. r=ron

Makes a naive './configure && make check' pass out of the box.
Prefer 'return' to 'exit' in the test main(). r=ron