libavcodec: Implementation of 32 bit fixed point FFT

Iterative implementation of 32 bit fixed point split-radix FFT.
Max FFT that can be calculated currently is 2^12.

Signed-off-by: Nedeljko Babic <nbabic@mips.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/fft-test.c

@@ -54,6 +54,10 @@
 #   define RANGE 1.0
 #   define REF_SCALE(x, bits)  (x)
 #   define FMT "%10.6f"
+#elif CONFIG_FFT_FIXED_32
+#   define RANGE 8388608
+#   define REF_SCALE(x, bits) (x)
+#   define FMT "%6d"
 #else
 #   define RANGE 16384
 #   define REF_SCALE(x, bits) ((x) / (1<<(bits)))