Rename CONFIG_FFT_FLOAT ---> FFT_FLOAT

The define does not originate from configure, so it should not
have a name that is CONFIG_-prefixed.
examples/decoding_encoding: fix style nits
Merge commit '794fcf79a89eca2d4e889803b2c804a0b1defbb3'

* commit '794fcf79a89eca2d4e889803b2c804a0b1defbb3':
  Rename CONFIG_FFT_FLOAT ---> FFT_FLOAT

Conflicts:
	libavcodec/fft-internal.h
	libavcodec/fft-test.c
	libavcodec/fft_fixed.c
	libavcodec/fft_float.c
	libavcodec/fft_template.c
	libavcodec/mdct_fixed.c
	libavcodec/mdct_float.c

Merged-by: Michael Niedermayer <michaelni@gmx.at>
rename CONFIG_FFT_FIXED_32 -> FFT_FIXED_32

This matches FFT_FLOAT

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