This refines the segment boundaries.  Based on code originally by Lukas Burget from Brno.

avoids cudafeat build failures with some CUDA toolkit versions

makes interface of HashList more standard; slight speed improvement.  Fixed version of #3402

This reverts commit 5cc7ce06.

This is turned on by using the option
--gpu-feature-extract=true.  By default this is on.  We provie the
option to turn it off because in situations where CPU resources
are unconfined you can get slightly higher performance with CPU
feature extraction but in most cases GPU feature extraction is faster
and has more stable performance.  In addition a user may wish to
turn it off to support models where feature extraction is currently
incomplete (e.g. FBANK, PLP, PITCH, etc).  We will add those
features in the future but for now a user wanted to decode those
models should place feature extraction on the host.

makes interface of HashList more standard; slight speed improvement.

Currently only supports MFCC features.

bash test `-f` does not work for `phones/` which is a directory. Changed it to `-e`.