Port equalizer plugin to 0.10 (#403572).

Port equalizer plugin to 0.10 (#403572).

Original commit message from CVS:
Patch by: James "Doc" Livingston  <doclivingston at gmail com>
* configure.ac:
* gst/equalizer/Makefile.am:
* gst/equalizer/gstiirequalizer.c: (gst_iir_equalizer_get_type),
(gst_iir_equalizer_base_init), (gst_iir_equalizer_class_init),
(gst_iir_equalizer_compute_frequencies),
(gst_iir_equalizer_set_property),
(gst_iir_equalizer_filter_inplace), (gst_iir_equalizer_setup),
(plugin_init):
Port equalizer plugin to 0.10 (#403572).