gst-plugins0.8 and gst-plugins0.8-* respectively. This is to leave room
for gstreamer 0.10 (which will be added with versioned names too, to avoid
annoying renames in the future).
While here, do some changes:
- Make gstreamer0.8 use the alternatives system to provide the unversioned
gst-* utilities.
- Rename all internal variables to have 0.8 in them to make it clear which
package they belong to.
