Update Alsa crate to 0.9.0

I updated my Raspberry Pi (but not the Kernel, since that one still has
the breaking change that breaks changing params), but without any
configuration changes, I now run into this crash:

    ALSA lib confmisc.c:1377:(snd_func_refer) Unable to find definition 'cards.2.pcm.front.0:CARD=2'
    ALSA lib conf.c:5204:(_snd_config_evaluate) function snd_func_refer returned error: No such file or directory
    ALSA lib conf.c:5727:(snd_config_expand) Evaluate error: No such file or directory
    ALSA lib pcm.c:2721:(snd_pcm_open_noupdate) Unknown PCM front:2
    thread 'playback' panicked at 'TODO: Failed to open device.: Error("snd_pcm_open", ENOENT)', src/playback.rs:358:50

The device is present, and I didn't change the configuration, so I
assume Alsa or the Kernel had a breaking change. But before I downgrade
again, maybe updating the Alsa crate fixes things? I don't have very
high hopes, but let's try. Also, this is one of the very few updates
that _removes_ dependencies, so that's a welcome change too.

Cargo.toml

@@ -5,7 +5,7 @@ authors = ["Ruud van Asseldonk <[email protected]>"]
 edition = "2018"
 
 [dependencies]
-alsa                  = "0.6.0"
+alsa                  = "0.9.0"
 bs1770                = "1.0.0"
 chrono                = "0.4.13"
 crossbeam             = "0.3"

src/playback.rs

@@ -25,6 +25,8 @@ use crate::history::PlaybackEvent;
 use crate::player::{Format, Millibel, PlayerState};
 use crate::prim::Hertz;
 
+const EBUSY: i32 = 16;
+
 type Result<T> = result::Result<T, alsa::Error>;
 
 fn print_available_cards() -> Result<()> {
@@ -90,7 +92,7 @@ fn open_device(card_name: &str) -> Result<(alsa::PCM, alsa::Mixer)> {
     let non_block = false;
     let pcm = match alsa::PCM::new(&device, alsa::Direction::Playback, non_block) {
         Ok(pcm) => pcm,
-        Err(error) if error.errno() == alsa::nix::errno::Errno::EBUSY => {
+        Err(error) if error.errno() == EBUSY => {
             println!("Could not open audio interface for exclusive access, it is already use.");
             return Err(error);
         }