Use printf-like format in JitRegister::Register

The API is cleaner (no more magic default parameter) and more
extensible like this.

Source/Core/Common/JitRegister.h

@@ -11,6 +11,6 @@ namespace JitRegister
 void Init();
 void Shutdown();
 void Register(const void* base_address, u32 code_size,
-	const char* name, u32 original_address=0);
+	const char* format, ...);
 
 }