Log Message:
Split aumix into two different packages:
- aumix 2.8nb6, which only provides ncurses support.  Note that its revision
  is bumped to note the differences from the previous package.
- aumix-gtk 2.8, which includes GTK 2.x and ncurses support.  While here,
  add a missing build dependency on pkgconfig.

The descriptions have also been rewritten to note the differences.

Addresses PR pkg/27340.