Configure filter for integer filtering

`set2int(h)`

set2int(h,coeffwl)

set2int(...,inwl)

g = set2int(...)

This section applies to discrete-time (`dfilt`

)
filters.

`set2int(h)`

scales the filter
coefficients to integer values and sets the filter coefficient and
input fraction lengths to zero.

`set2int(h,coeffwl)`

uses
the number of bits specified by `coeffwl`

as the
word length it uses to represent the filter coefficients.

`set2int(...,inwl)`

uses
the number of bits specified by `coeffwl`

as the
word length it uses to represent the filter coefficients and the number
of bits specified by `inwl`

as the word length to
represent the input data.

`g = set2int(...)`

returns
the gain `g`

introduced into the filter by scaling
the filter coefficients to integers. `g`

is always
calculated to be a power of 2.

`set2int`

does not work with CIC decimators
or interpolators because they do not have coefficients.