Fix a number of other qdoc issues.

* Several places needed the forward class declaration hack
* Missing/wrong minor version numbers on imports
* A few typos
* Any number of attempts to work around qdoc
* A few missing docs
* Tweaked soundeffect docs

Change-Id: I3c2ab998a11cbb0956712e0423e01fdb70f5bfff
Reviewed-by: Peter Yard <peter.yard@nokia.com>
Reviewed-by: Angus Cummings <angus.cummings@nokia.com>
Reviewed-by: Jonas Rabbe <jonas.rabbe@gmail.com>

src/multimedia/audio/qaudiodecoder.cpp

@@ -368,8 +368,6 @@ QtMultimedia::SupportEstimate QAudioDecoder::hasSupport(const QString &mimeType,
 }
 
 /*!
-    \fn QAudioDecoder::bufferAvailable() const
-
     Returns true if a buffer is available to be read,
     and false otherwise.  If there is no buffer available, calling
     the \l read() function will return an invalid buffer.
@@ -549,6 +547,11 @@ QAudioBuffer QAudioDecoder::read() const
     \brief the active filename being decoded by the decoder object.
 */
 
+/*!
+    \property QAudioDecoder::bufferAvailable
+    \brief whether there is a decoded audio buffer available
+*/
+
 #include "moc_qaudiodecoder.cpp"
 QT_END_NAMESPACE