Add an echo/reverb filter to the audiofx plugin, with configurable echo delay, intens...

Add an echo/reverb filter to the audiofx plugin, with configurable echo delay, intensity and feedback. Fixes bug #567...

Original commit message from CVS:
* docs/plugins/Makefile.am:
* docs/plugins/gst-plugins-good-plugins-docs.sgml:
* docs/plugins/gst-plugins-good-plugins-sections.txt:
* docs/plugins/gst-plugins-good-plugins.args:
* docs/plugins/gst-plugins-good-plugins.hierarchy:
* docs/plugins/inspect/plugin-audiofx.xml:
* docs/plugins/inspect/plugin-spectrum.xml:
* gst/audiofx/Makefile.am:
* gst/audiofx/audiofx.c: (plugin_init):
* gst/audiofx/audioreverb.c: (gst_audio_reverb_base_init),
(gst_audio_reverb_class_init), (gst_audio_reverb_init),
(gst_audio_reverb_finalize), (gst_audio_reverb_set_property),
(gst_audio_reverb_get_property), (gst_audio_reverb_setup),
(gst_audio_reverb_stop), (gst_audio_reverb_transform_ip):
* gst/audiofx/audioreverb.h:
* tests/check/Makefile.am:
* tests/check/elements/audioreverb.c: (setup_reverb),
(cleanup_reverb), (GST_START_TEST), (audioreverb_suite):
Add an echo/reverb filter to the audiofx plugin, with configurable
echo delay, intensity and feedback. Fixes bug #567874.