hdajackretask: Add "hints" functionality

The kernel driver has some hints you can send to it that changes
parser behaviour. This patch exposes that functionality to the user.

(This patch also includes minor fixes for documentation, GTK warnings
and whitespace.)

Signed-off-by: David Henningsson <david.henningsson@canonical.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>