- Change computeGrad and self.computeGrad to compute_grad
- Add compute_grad to props in ConnectionistTemporalClassification
- Add dummy OpenMP Op to pull headers and configuration parameters when
  OpenMP is enabled, so that it can be used inside the C wrapper
- Add verification for when Baidu CTC is enabled using the config
  parameter ctc.enabled
- Change environment variable CTC_LIB for the config parameter
  ctc.root
Signed-off-by: João Victor Tozatti Risso <joaovictor.risso@gmail.com>