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=42da990859d41a4da9f74e4d20fe5c5b972ada18'>root</a>/<a href='/guix/log/gnu?id=42da990859d41a4da9f74e4d20fe5c5b972ada18'>gnu</a>/<a href='/guix/log/gnu/packages?id=42da990859d41a4da9f74e4d20fe5c5b972ada18'>packages</a>/<a href='/guix/log/gnu/packages/popt.scm?id=42da990859d41a4da9f74e4d20fe5c5b972ada18'>popt.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/popt.scm?id=42da990859d41a4da9f74e4d20fe5c5b972ada18&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2021-04-10 14:11:27 +0200'>2021-04-10</span></td><td><a href='/guix/commit/gnu/packages/popt.scm?id=80a63aefc2f39fd63b9624c0d1cb579c99cdf518'>gnu: popt: Fix typo in description.</a><span class='msg-avail'>...</span></td><td>Tobias Geerinckx-Rice</td></tr>
<tr><td><span title='2020-07-25 16:16:11 +0200'>2020-07-25</span></td><td><a href='/guix/commit/gnu/packages/popt.scm?id=e605d3bd54118605281a472c97db3d74e7b97b63'>gnu: popt: Update to 1.18.</a><span class='msg-avail'>...</span></td><td>Marius Bakke</td></tr>
<tr><td><span title='2020-07-12 23:08:15 +0200'>2020-07-12</span></td><td><a href='/guix/commit/gnu/packages/popt.scm?id=b0e7b6992f3f845e83cfbca4d700b51dba50b4d5'>gnu: Remove ".git" from "https://github/…/….git".</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2020-05-29 23:11:37 +0200'>2020-05-29</span></td><td><a href='/guix/commit/gnu/packages/popt.scm?id=91c8b23e571b90e2d263194c9fbb2b05c0475dc1'>gnu: popt: Remove defunct mirror.</a><span class='msg-avail'>...</span></td><td>Marius Bakke</td></tr>