This is used to avoid dynalloc doing silly things on periodic LSB
patterns and to reduce the bitrate on near-silence.

tf_estimate was being initialized to zero and then never set because
transient_analysis() wasn't being called. This could also have affected
other frame sizes at lower complexity.

atan2() is replaced by Monty's approximation.

This was found to cause a quality regression (e.g. in the velvet sample)

Tuned the tonality estimator to trigger on signals where only part of the
spectrum is tonal. Also tuned the pitch detector not to be confused
by short-term correlation.

- New DC rejection filter that avoids numerical issues
- Higher cap on HF dynalloc
- Proper filter memory for transient detector
- Prevents transient detector from detecting low-freq tones as transients

Fixes two leakage problems on the wood blocks sample
- Removes DC which causes leakage with no masking
- Detect leakage by comparing short-MDCT energy to long-MDCT energy
  and boost allocation for bands with leakage

Haven't tested it much and not sure not to use it without risk
for high-quality streams that may change bandwidth

Also, reducing the VBR rate on panned mono

Should be mostly usable now.

Conflicts:

	src/opus_encoder.c