Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

Add some parameters to existing function documentation.
Remove some unneeded documentation.
Convert some static function documentation to non-doxygen style.

Update FATE references accordingly.

scale_coefficients() rather than in apply_channel_coupling()

The number of rematrixing bands still needs to be calculated.

This is faster than using the clip_coefficients() function. Also,
clipping the coordinates before determining reuse is better since it
will compare coordinates that are closer to their final encoded values.

channel.

Move bit counting to the bit allocation function. Move exponent grouping to
after bit allocation. This will allow for adjustment of bandwidth parameters
during bit allocation without having to do exponent grouping multiple times.

Since both the fixed-point and floating-point encoders use the FFTContext,
this no longer needs to be in a separate context. Also, when a short-transform
context is added, the same MDCT window will be used.

This ensures that any processing between the MDCT and exponent extraction will
be using clipped coefficients.

This avoids using function pointers for quite a few small functions, most of
which just call DSP functions.

This fixes a segfault when using the C version of ac3dsp.float_to_fixed24().

sizeof(SampleType) is different for fixed and float encoders.

Function pointers are used for templated functions instead of needlessly
duplicating many functions.