Use fabsf instead of fabs.

We are starting with a float and the function call takes a float.

This avoids a float->double->float cast when calculating coefficients.
resample.c - broaden the filter more aggressively.

When calculating how many taps to use, we now round up to the nearest
even number.

Before, we woere not broadening the filter enough in some cases and
this led to some aliasing effects.