BlackBerry/QNX: Add a new backend for Blackberry handling audio

For now it only implements the audio output part.
The plugin can be used on all QNX systems (including BB10) that
provide a libasound version < 1.0.10.

Change-Id: Ifcfd871558d5d2bfb9e8a5f5ef0cfe009c0a111d
Reviewed-by: Thomas McGuire <thomas.mcguire@kdab.com>

src/plugins/plugins.pro

@@ -12,6 +12,10 @@ blackberry {
     SUBDIRS += blackberry
 }
 
+qnx {
+    SUBDIRS += qnx
+}
+
 win32 {
     SUBDIRS += audiocapture
 }