add alsa configuration

enable dmix and dsnoop. Now we can play and record with multiple application simultaneously.

asound.conf

@@ -0,0 +1,34 @@
+# The IPC key of dmix or dsnoop plugin must be unique
+# If 555555 or 666666 is used by other processes, use another one
+
+pcm.!default {
+    type asym
+    playback.pcm "playback"
+    capture.pcm "capture"
+}
+
+pcm.playback {
+    type plug
+    slave.pcm "dmixed"
+}
+
+pcm.capture {
+    type plug
+    slave.pcm "array"
+}
+
+pcm.dmixed {
+    type dmix
+    slave.pcm "hw:0,0"
+    ipc_key 555555 
+}
+
+pcm.array {
+    type dsnoop
+    slave {
+        pcm "hw:0,0"
+        channels 2
+    }
+    ipc_key 666666
+}
+