float-dsp-test: do not use C99's predefined  __func__

It is not supported by all compilers on FATE. Fixes "some test were
skipped" errors.
Merge remote-tracking branch 'qatar/master'

* qatar/master:
  float-dsp-test: do not use C99's predefined  __func__

Merged-by: Michael Niedermayer <michaelni@gmx.at>
configure: fix direct symbol ref support detection

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