spearmint: Fix repeatedly overbrighting the light grid

Running vid_restart repeatedly in a map caused the ambient light to
increase as reported by r_debugLight 1. (It stops at 255 bightness and
normalizes the color.)

Spearmint's BSP abstraction layer shares the same BSP data for collision
and the renderer. The renderer applied overbright to the bspFile_t
light grid data each time it registered the map causing the changes to
persist across vid_restart.

The renderer now allocates memory for overbright light grid.

code/renderergl1/tr_bsp.c

@@ -1985,11 +1985,13 @@ void R_LoadLightGrid( const bspFile_t *bsp ) {
 		return;
 	}
 
-	w->lightGridData = bsp->lightGridData;
+	w->lightGridData = ri.Hunk_Alloc( bsp->numGridPoints * 8, h_low );
 	w->numGridPoints = bsp->numGridPoints;
 	w->lightGridArray = bsp->lightGridArray;
 	w->numGridArrayPoints = bsp->numGridArrayPoints;
 
+	Com_Memcpy( w->lightGridData, bsp->lightGridData, bsp->numGridPoints * 8 );
+
 	// deal with overbright bits
 	for ( i = 0 ; i < bsp->numGridPoints ; i++ ) {
 		R_ColorShiftLightingBytes( 4, &w->lightGridData[i*8], &w->lightGridData[i*8] );

code/renderergl2/tr_bsp.c

@@ -2533,11 +2533,13 @@ void R_LoadLightGrid( const bspFile_t *bsp ) {
 		return;
 	}
 
-	w->lightGridData = bsp->lightGridData;
+	w->lightGridData = ri.Hunk_Alloc( bsp->numGridPoints * 8, h_low );
 	w->numGridPoints = bsp->numGridPoints;
 	w->lightGridArray = bsp->lightGridArray;
 	w->numGridArrayPoints = bsp->numGridArrayPoints;
 
+	Com_Memcpy( w->lightGridData, bsp->lightGridData, bsp->numGridPoints * 8 );
+
 	// deal with overbright bits
 	for ( i = 0 ; i < bsp->numGridPoints ; i++ ) {
 		R_ColorShiftLightingBytes( 4, &w->lightGridData[i*8], &w->lightGridData[i*8] );