logging with kissfft

[peter-toft-greve]

Hi Mark

I have fiddling with many DSP platforms where KISSFFT does a good job - THANX A MIL.
But I have now seen some platforms with a quite string handling.

Can I with charm, sneaky tactics, and flatter ask you to change
https://github.com/mborgerding/kissfft/blob/master/kiss_fft_log.h#L20
from
#if defined(NDEBUG)
to
#if defined(NDEBUG) || defined(KIFFFFT_NO_LOG)

or similar - the naming etc I leave up to you.

The problem is that Debug builds will fail if not prohibited with a KISSFFT-specific compile flag.

Again thank you - U rock.

/pto