While calculation the best pitch delay (bestIntPitchDelay) the lower bounds of range was not calculated correctly near the maximun range.

codebookqLSF check started on index 1 instead of index 0

- past autocorrelation coefficients can't be 0, set autocorrelation[0]
to 1 for the whole past buffer.

- VAD algo is actually the variant described in G729 Appendix II
+ move headers to src files

Possible division by 0, check on operand values must be done on the scaled
ones used as denominator.