Max pitch gain allowed is now 0.625.

Even if there's still lots of float operations left.

Also increasing the gain slightly.

Post-filter now delays the filter coefs by the overlap so that the pre-filter
and post-filter are synchronised.

So far, only the post-filter is there.

Oops. The deemphasis was called on the wrong signal!

Fix crashes with VBR for short duration frames and very low bitrates. This may, however, cause the encoder to violate the rate target at insanely low rates.

This also generally improves VBR behavior by more carefully accounting
for rounding.

Switch example tools to use VBR and 960 sample frames by default on the basis that if the user doesn't have any particular requirements that they probably want this.

Minor change in the VBR behavior to hot-start with some internal state
parameters which were observed to be quite consistent across bitrates,
framesizes, and content. This also prevents it from completely burning
the reserve capacity on the first frame if its a short.

Also switch some maximum frame sizes to match the OPUS draft maximums.

Also making use of alloc_trim_analysis() again because the effect of
inter-channel correlation on the bitstream is really in terms of absolute
number of bits/samples.

The idea here is that it's better to fold a higher band -- even if it was
coded less accurately -- than a lower band that may have a different
temporal structure.

Also fixed a fixed-point breakage.

Previous limit was effectively 120.