WP2030 - sine.c cleanup

[drowe67]

• review source code and comments
• Hamming -> Hann window
• some tests, e.g. estimate amplitude on sine wave, analysis/synthesis test with contrived pitch
• check variable names match codec2.pdf
• consider making trapezoidal window function a triangular function, as I think with TW == 0.05 that is effectively what we are doing.
• consider making notation a bit more consistent, e.g. n for time index, k for DFT index, m for harmonic index
• In v est function distinguish Am from model->A
• decide between phi (source code) for phase or theta (latex), it should be consistent