Work around conflicting declaration of gamma

FossilOrigin-Name: 7c3936be15500a3bdaa3aa603479e02786123f92c9f697b4a420d3b7411aa998

src/cube.h

@@ -2,9 +2,7 @@
 
 #import <ObjFW/ObjFW.h>
 
-#define gamma gamma__
 #include <SDL2/SDL.h>
-#undef gamma
 
 #include "tools.h"
 

src/rendergl.m

@@ -1,5 +1,7 @@
 // rendergl.cpp: core opengl rendering stuff
 
+#define gamma math_gamma
+
 #include "cube.h"
 
 #import "Command.h"
@@ -324,6 +326,8 @@ addstrip(int tex, int start, int n)
 	[strips addItem:&s];
 }
 
+#undef gamma
+
 VARFP(gamma, 30, 100, 300, {
 	float f = gamma / 100.0f;
 	Uint16 ramp[256];

src/tools.h

@@ -3,16 +3,8 @@
 #ifndef _TOOLS_H
 #define _TOOLS_H
 
-#ifdef __GNUC__
-# define gamma __gamma
-#endif
-
 #include <math.h>
 
-#ifdef __GNUC__
-# undef gamma
-#endif
-
 #include <assert.h>
 #include <limits.h>
 #include <stdarg.h>