Core/DSPCore: Extended opcode handling fixes

* Make writeToBackLog private to DSPIntExtOps.cpp 
  (JIT variants of 'l and 'ln are disabled and broken as is)
* Make zeroing of the backlog conditional on doing an interpreter fallback and
  do it at a few more places
* Fix selection of cleanup for extended opcodes.
* Fix the DSP unit tests to correctly emit the function prolog/epilog
  (else EBX wouldn't be saved)
* Add a few more DSP unit tests


git-svn-id: https://dolphin-emu.googlecode.com/svn/trunk@6325 8ced0084-cf51-0410-be5f-012b33b47a6e

Source/Core/DSPCore/Src/DSPEmitter.h

@@ -64,6 +64,7 @@ public:
 	void popExtValueToReg();
 	void pushExtValueFromMem(u16 dreg, u16 sreg);
 	
+	void zeroWriteBackLog(const UDSPInstruction opc);
 	// Ext commands
 	void l(const UDSPInstruction opc);
 	void ln(const UDSPInstruction opc);