Prevent a name clash

--- gdl-v1.0.6/src/plotting_shade_surf.cpp.org	2024-05-23 16:36:39.000000000 +0200
+++ gdl-v1.0.6/src/plotting_shade_surf.cpp	2024-05-30 09:56:41.415618734 +0200
@@ -430,11 +430,11 @@
 
         //position of light Source. Plplot does not use only the direction of the beam but the position of the illuminating
         //source. And its illumination looks strange. We try to make the ill. source a bit far in the good direction.
-        PLFLT sun[3];
-        sun[0]=lightSourcePos[0]*1E10;
-        sun[1]=lightSourcePos[1]*1E10;
-        sun[2]=lightSourcePos[2]*1E10;if (below) sun[2]*=-1;
-        actStream->lightsource(sun[0],sun[1],sun[2]);
+        PLFLT sunn[3];
+        sunn[0]=lightSourcePos[0]*1E10;
+        sunn[1]=lightSourcePos[1]*1E10;
+        sunn[2]=lightSourcePos[2]*1E10;if (below) sunn[2]*=-1;
+        actStream->lightsource(sunn[0],sunn[1],sunn[2]);
         actStream->surf3d(xg1,yg1,map,cgrid1.nx,cgrid1.ny,meshOpt,NULL,0);
 
 //Clean allocated data struct