Merge branch 'exp_improved_simd2'

dnn/README.md

dnn/autogen.sh

dnn/causalconv.py

dnn/configure.ac

dnn/dump_data.c

dnn/dump_lpcnet.py

dnn/gatedconv.py

dnn/lpcnet.py

dnn/mdense.py

dnn/nnet.c

dnn/nnet.h

dnn/tansig_table.h

dnn/train_lpcnet.py

dnn/training_tf2/dump_lpcnet.py

dnn/training_tf2/lpcnet.py

dnn/training_tf2/pade.py

dnn/training_tf2/test_lpcnet.py

dnn/training_tf2/train_lpcnet.py

dnn/ulaw.py

dnn/vec.h