More warning fixes.

RageThreads.h is right now clear of
Effective Violations. It may be worth studying.

src/RageSoundReader_Preload.cpp

@@ -34,7 +34,8 @@ bool RageSoundReader_Preload::PreloadSound( RageSoundReader *&pSound )
 }
 
 RageSoundReader_Preload::RageSoundReader_Preload():
-	m_Buffer( new RString )
+	m_Buffer( new RString ), m_bBufferIs16Bit(false),
+	m_iPosition(0), m_iSampleRate(0), m_iChannels(0), m_fRate(0.0f)
 {
 	m_bBufferIs16Bit = g_bSoundPreload16bit.Get();
 }