Allow SheetBuilder to generate 1/2/4 channel sheets.

This makes the SpriteFont RBGA sprite hack explicit,
and adds a DualIndexed option to be used by the voxel
renderer.

OpenRA.Game/Graphics/SpriteFont.cs

@@ -31,8 +31,10 @@ namespace OpenRA.Graphics
 			glyphs = new Cache<Pair<char, Color>, GlyphInfo>(CreateGlyph, 
 			         Pair<char,Color>.EqualityComparer);
 
-			// setup a 1-channel SheetBuilder for our private use
-			if (builder == null) builder = new SheetBuilder(TextureChannel.Alpha);
+			// setup a SheetBuilder for our private use
+			// TODO: SheetBuilder state is leaked between mod switches
+			if (builder == null)
+				builder = new SheetBuilder(SheetType.BGRA);
 
 			PrecacheColor(Color.White);
 			PrecacheColor(Color.Red);
@@ -46,7 +48,7 @@ namespace OpenRA.Graphics
 					throw new InvalidOperationException();
 		}
 
-		public void DrawText (string text, float2 location, Color c)
+		public void DrawText(string text, float2 location, Color c)
 		{
 			location.Y += size;	// baseline vs top
 
@@ -84,7 +86,7 @@ namespace OpenRA.Graphics
 
 		public int2 Measure(string text)
 		{
-			return new int2((int)text.Split( '\n' ).Max( s => s.Sum(a => glyphs[Pair.New(a, Color.White)].Advance)), text.Split('\n').Count()*size);
+			return new int2((int)text.Split('\n').Max(s => s.Sum(a => glyphs[Pair.New(a, Color.White)].Advance)), text.Split('\n').Count()*size);
 		}
 
 		Cache<Pair<char,Color>, GlyphInfo> glyphs;