ext/libvisual/visual.c: update to work also with libvisual 0.4 API

ext/libvisual/visual.c: update to work also with libvisual 0.4 API

Original commit message from CVS:
* ext/libvisual/visual.c: (gst_vis_src_negotiate),
(gst_visual_chain), (gst_visual_change_state):
update to work also with libvisual 0.4 API
* tools/gst-launch-ext.1.in:
* tools/gst-visualise.1.in:
remove references to old man-pages
* tests/examples/seek/seek.c: (main):
add real meadi-buttons, add tool-tips for the seek-options, arrange
seek options in a table