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_EStreamModes.h

@@ -0,0 +1,31 @@
+// 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 __E_IRRKLANG_STREAM_MODES_H_INCLUDED__
+#define __E_IRRKLANG_STREAM_MODES_H_INCLUDED__
+
+namespace irrklang  
+{
+	//! An enumeration for all types of supported stream modes
+	enum E_STREAM_MODE
+	{
+		//! Autodetects the best stream mode for a specified audio data.
+		ESM_AUTO_DETECT = 0,
+
+		//! Streams the audio data when needed.
+		ESM_STREAMING,
+
+		//! Loads the whole audio data into the memory.
+		ESM_NO_STREAMING,
+
+		//! This enumeration literal is never used, it only forces the compiler to 
+		//! compile these enumeration values to 32 bit.
+		ESM_FORCE_32_BIT = 0x7fffffff
+	};
+
+} // end namespace irrklang
+
+
+#endif
+