configure.ac: export [_]*{gst,Gst,GST}.* symbols from plugins

configure.ac: export [_]*{gst,Gst,GST}.* symbols from plugins

Original commit message from CVS:
2004-02-22  Benjamin Otte  <otte@gnome.org>

* configure.ac:
export [_]*{gst,Gst,GST}.* symbols from plugins

2004-02-22  Christophe Fergeau <teuf@gnome.org>

reviewed by: Benjamin Otte  <otte@gnome.org>

* ext/lame/gstlame.c: (add_one_tag):
* ext/mad/gstid3tag.c: (gst_mad_id3_to_tag_list):
* ext/vorbis/vorbisenc.c: (gst_vorbisenc_get_tag_value),
(gst_vorbisenc_metadata_set1):
* gst/tags/gstid3tag.c:
* gst/tags/gstvorbistag.c: (gst_vorbis_tag_add):
apply fixes from bugs #135042 (lame can't write tags) and #133817
(add GST_ALBUM_VOLUME_{COUNT,NUMBER} tags)