goertzel.h : Remove the default constructor for fft::goertzel.

The default constructor does not properly initialize the class
variables. This leads to the possibilty of undefined behavior if
the class is used carelessly. Instead force the user to do the right
thing at compile time.

The patch also fixes the in-tree user of this class.

Signed-off-by: Philip Balister <philip@opensdr.com>
Merge branch 'maint'