The simple mixer abstraction - more work

- separated the "base library" from ac97.c (dynamically loaded)
  - added necessary handling of all private structures
  - added selector and sid registration functions and handling code
- added basic code for hda.c (yeah, my notebook has this hw)

src/conf/smixer.conf

@@ -6,3 +6,7 @@ ac97 {
 	searchl "AC97a:"
 	lib smixer-ac97.so
 }
+hda {
+	searchl "HDA:"
+	lib smixer-hda.so
+}