add snd_device_name_hint() function and initial implementation

- add snd_device_name_hint() and snd_device_name_free_hint() functions
- add snd_ctl_iface_conf_name() functions
- do not accept parameters for the plugin definition without @args section
- add defaults.pcm.dmix.card/device and dsnoop.card/device definitions
- add hints for HDA-Intel.conf, pcm/dmix.conf, pcm/dsnoop.conf and alsa.conf
- add test/namehint test utility
- doxygen related cleanups

src/conf/cards/ICH-MODEM.conf

@@ -12,4 +12,5 @@ ICH-MODEM.pcm.modem.0 {
 	type hw
 	card $CARD
 	device 0
+	hint 0
 }