Reorder TileLayer. (#5638)

Despite the split of TileSpec into TileDef and TileLayer, the
TileLayer struct is still 66 bytes large, and doesn't fit in
a single cacheline.

I'm moving the color member to cacheline 2, in the hope that it
is less used and the compiler loads all the hot members in a single
cacheline instead. Only color sits now in cacheline 2, all the
other members are in cacheline 1.

Note: is_color is probably rarely set, most nodes will likely
not use hardware coloring, but this may change in the future.
Ideally, this class is shrunk to 64 bytes.

src/client/tile.h

@@ -201,21 +201,21 @@ struct TileLayer
 {
 	TileLayer():
 		texture(NULL),
+		normal_texture(NULL),
+		flags_texture(NULL),
+		shader_id(0),
 		texture_id(0),
-		color(),
+		animation_frame_length_ms(0),
+		animation_frame_count(1),
 		material_type(TILE_MATERIAL_BASIC),
 		material_flags(
 			//0 // <- DEBUG, Use the one below
 			MATERIAL_FLAG_BACKFACE_CULLING |
 			MATERIAL_FLAG_TILEABLE_HORIZONTAL|
 			MATERIAL_FLAG_TILEABLE_VERTICAL
 		),
-		shader_id(0),
-		normal_texture(NULL),
-		flags_texture(NULL),
-		animation_frame_length_ms(0),
-		animation_frame_count(1),
-		has_color(false)
+		has_color(false),
+		color()
 	{
 	}
 
@@ -286,27 +286,32 @@ struct TileLayer
 			&& (material_flags & MATERIAL_FLAG_TILEABLE_VERTICAL);
 	}
 
+	// Ordered for size, please do not reorder
+
 	video::ITexture *texture;
-	u32 texture_id;
-	/*!
-	 * The color of the tile, or if the tile does not own
-	 * a color then the color of the node owning this tile.
-	 */
-	video::SColor color;
-	// Material parameters
-	u8 material_type;
-	u8 material_flags;
-	u32 shader_id;
 	video::ITexture *normal_texture;
 	video::ITexture *flags_texture;
 
-	// Animation parameters
+	u32 shader_id;
+
+	u32 texture_id;
+
 	u16 animation_frame_length_ms;
 	u8 animation_frame_count;
+
+	u8 material_type;
+	u8 material_flags;
+
 	//! If true, the tile has its own color.
 	bool has_color;
 
 	std::vector<FrameSpec> frames;
+
+	/*!
+	 * The color of the tile, or if the tile does not own
+	 * a color then the color of the node owning this tile.
+	 */
+	video::SColor color;
 };
 
 /*!