Change CMakeLists.txt to add 2d_game project, and added irrKlang to LIBS.

Added irrKlang.dll and ikpMP2.dll to dlls folder.  Added irrKlang as a
sub-folder under includes.  Added irrKlang.lib to lib folder.  At this point
running cmake gave an error it couldn't find source files under 2d_game.
Moved 2d_game source up one folder level, then cmake found the files.

includes/irrKlang/ik_IFileReader.h

@@ -0,0 +1,50 @@
+// Copyright (C) 2002-2018 Nikolaus Gebhardt
+// This file is part of the "irrKlang" library.
+// For conditions of distribution and use, see copyright notice in irrKlang.h
+
+#ifndef __I_IRRKLANG_READ_FILE_H_INCLUDED__
+#define __I_IRRKLANG_READ_FILE_H_INCLUDED__
+
+#include "ik_IRefCounted.h"
+
+namespace irrklang
+{
+
+	//! Interface providing read acess to a file.
+	class IFileReader : public virtual IRefCounted
+	{
+	public:
+
+		virtual ~IFileReader() {};
+
+		//! Reads an amount of bytes from the file.
+		//! \param buffer: Pointer to buffer where to read bytes will be written to.
+		//! \param sizeToRead: Amount of bytes to read from the file.
+		//! \return Returns how much bytes were read.
+		virtual ik_s32 read(void* buffer, ik_u32 sizeToRead) = 0;
+
+		//! Changes position in file, returns true if successful.
+		//! \param finalPos: Destination position in the file.
+		//! \param relativeMovement: If set to true, the position in the file is
+		//! changed relative to current position. Otherwise the position is changed 
+		//! from beginning of file.
+		//! \return Returns true if successful, otherwise false.
+		virtual bool seek(ik_s32 finalPos, bool relativeMovement = false) = 0;
+
+		//! Returns size of file.
+		//! \return Returns the size of the file in bytes.
+		virtual ik_s32 getSize() = 0;
+
+		//! Returns the current position in the file.
+		//! \return Returns the current position in the file in bytes.
+		virtual ik_s32 getPos() = 0;
+
+		//! Returns name of file.
+		//! \return Returns the file name as zero terminated character string.
+		virtual const ik_c8* getFileName() = 0;
+	};
+
+} // end namespace irrklang
+
+#endif
+