Patch to work around incompatibility between irrlicht-1.8.1 and mesa-10.x.
Upstream bug (fixed in trunk): http://sourceforge.net/p/irrlicht/bugs/429/
Upstream fix: http://sourceforge.net/p/irrlicht/code/4810
This patch copied from:
http://sources.gentoo.org/cgi-bin/viewvc.cgi/gentoo-x86/dev-games/irrlicht/files/irrlicht-1.8.1-mesa-10.x.patch?view=markup

From 244d00280c1b082ca164f92337773e9e4e1a3898 Mon Sep 17 00:00:00 2001
From: hiker <henrichsjoerg@mgail.com>
Date: Wed, 26 Feb 2014 11:13:03 +1100
Subject: [PATCH] Applied patch from jpirie for fixing mesa 10 compilation
 problems.

--- irrlicht-1.8.1/source/Irrlicht/COpenGLExtensionHandler.h
+++ irrlicht-1.8.1/source/Irrlicht/COpenGLExtensionHandler.h
@@ -21,6 +21,7 @@
 	#endif
 	#include <GL/gl.h>
 	#if defined(_IRR_OPENGL_USE_EXTPOINTER_)
+		typedef void (APIENTRYP PFNGLBLENDEQUATIONPROC) (GLenum mode);
 		#include "glext.h"
 	#endif
 	#include "wglext.h"
@@ -35,6 +36,7 @@
 	#endif
 	#include <OpenGL/gl.h>
 	#if defined(_IRR_OPENGL_USE_EXTPOINTER_)
+		typedef void (APIENTRYP PFNGLBLENDEQUATIONPROC) (GLenum mode);
 		#include "glext.h"
 	#endif
 #elif defined(_IRR_COMPILE_WITH_SDL_DEVICE_) && !defined(_IRR_COMPILE_WITH_X11_DEVICE_)
@@ -48,6 +50,7 @@
 	#define NO_SDL_GLEXT
 	#include <SDL/SDL_video.h>
 	#include <SDL/SDL_opengl.h>
+	typedef void (APIENTRYP PFNGLBLENDEQUATIONPROC) (GLenum mode);
 	#include "glext.h"
 #else
 	#if defined(_IRR_OPENGL_USE_EXTPOINTER_)
@@ -60,6 +63,7 @@
 	#include <GL/gl.h>
 	#include <GL/glx.h>
 	#if defined(_IRR_OPENGL_USE_EXTPOINTER_)
+	typedef void (APIENTRYP PFNGLBLENDEQUATIONPROC) (GLenum mode);
 	#include "glext.h"
 	#undef GLX_ARB_get_proc_address // avoid problems with local glxext.h
 	#include "glxext.h"
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<div class='path'>path: <a href='/guix/log/?id=b1d2e0b4e0a22c1cdda376b1c9950f14ca99230e'>root</a>/<a href='/guix/log/gnu?id=b1d2e0b4e0a22c1cdda376b1c9950f14ca99230e'>gnu</a>/<a href='/guix/log/gnu/packages?id=b1d2e0b4e0a22c1cdda376b1c9950f14ca99230e'>packages</a>/<a href='/guix/log/gnu/packages/slang.scm?id=b1d2e0b4e0a22c1cdda376b1c9950f14ca99230e'>slang.scm</a></div><div class='content'><table class='list nowrap'><tr class='nohover'><th class='left'>Age</th><th class='left'>Commit message (<a href='/guix/log/gnu/packages/slang.scm?id=b1d2e0b4e0a22c1cdda376b1c9950f14ca99230e&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2018-11-07 18:39:19 +0900'>2018-11-07</span></td><td><a href='/guix/commit/gnu/packages/slang.scm?id=8243f4e55a9f87821370eb2198fa9b5c8eac6648'>gnu: slang: Use a correct location for terminfo dirs.</a><span class='msg-avail'>...</span></td><td>Mathieu Othacehe</td></tr>
<tr><td><span title='2018-08-28 01:19:28 +0200'>2018-08-28</span></td><td><a href='/guix/commit/gnu/packages/slang.scm?id=eb87b634a7723111bdbc84f1971fe64bc96a8963'>gnu: slang: Update to 2.3.2.</a><span class='msg-avail'>...</span></td><td>Marius Bakke</td></tr>
<tr><td><span title='2018-03-16 09:08:31 -0400'>2018-03-16</span></td><td><a href='/guix/commit/gnu/packages/slang.scm?id=6cbee49d6668eb7fd738080666f66febfce8c7e8'>gnu: All snippets report errors using exceptions, else return #t.</a><span class='msg-avail'>...</span></td><td>Mark H Weaver</td></tr>
<tr><td><span title='2018-02-21 15:02:47 +0100'>2018-02-21</span></td><td><a href='/guix/commit/gnu/packages/slang.scm?id=61faf24df66bdade0ec780d4a5e5e3d461329341'>gnu: slang: Update to 2.3.1a.</a><span class='msg-avail'>...</span></td><td>Tobias Geerinckx-Rice</td></tr>
<tr><td><span title='2018-01-21 20:40:29 +0100'>2018-01-21</span></td><td><a href='/guix/commit/gnu/packages/slang.scm?id=982dab0ba73a8556bb5ab65bf199efbd1f2b508b'>gnu: newt: Update to 0.52.20.</a><span class='msg-avail'>...</span></td><td>Tobias Geerinckx-Rice</td></tr>