NESHawk - put sealed on some classes I missed sometime back when I did that

BizHawk.Emulation/Consoles/Nintendo/NES/APU.cs

@@ -21,7 +21,7 @@ namespace BizHawk.Emulation.Consoles.Nintendo
 
 	sealed partial class NES
 	{
-		public class APU 
+		public sealed class APU 
 		{
 			public static bool CFG_DECLICK = true;
 
@@ -76,7 +76,7 @@ namespace BizHawk.Emulation.Consoles.Nintendo
 			};
 
 
-			class PulseUnit
+			sealed class PulseUnit
 			{
 				public PulseUnit(APU apu, int unit) { this.unit = unit; this.apu = apu; }
 				public int unit;
@@ -291,7 +291,7 @@ namespace BizHawk.Emulation.Consoles.Nintendo
 				}
 			}
 
-			class NoiseUnit
+			sealed class NoiseUnit
 			{
 				APU apu;
 
@@ -451,7 +451,7 @@ namespace BizHawk.Emulation.Consoles.Nintendo
 				}
 			}
 
-			class TriangleUnit
+			sealed class TriangleUnit
 			{
 				//reg0
 				int linear_counter_reload, control_flag;
@@ -600,7 +600,7 @@ namespace BizHawk.Emulation.Consoles.Nintendo
 				}
 			} //class TriangleUnit
 
-			class DMCUnit
+			sealed class DMCUnit
 			{
 				APU apu;
 				int[] DMC_RATE;

BizHawk.Emulation/Consoles/Nintendo/NES/PPU.regs.cs

@@ -21,7 +21,7 @@ namespace BizHawk.Emulation.Consoles.Nintendo
 	{
 		sealed partial class PPU
 		{
-			public class Reg_2001
+			public sealed class Reg_2001
 			{
 				public Bit color_disable; //Color disable (0: normal color; 1: AND all palette entries with 110000, effectively producing a monochrome display)
 				public Bit show_bg_leftmost; //Show leftmost 8 pixels of background
@@ -67,7 +67,7 @@ namespace BizHawk.Emulation.Consoles.Nintendo
 
 			//uses the internal counters concept at http://nesdev.icequake.net/PPU%20addressing.txt
 			//TODO - this should be turned into a state machine
-			public class PPUREGS
+			public sealed class PPUREGS
 			{
 				PPU ppu;
 				public PPUREGS(PPU ppu)
@@ -267,7 +267,7 @@ namespace BizHawk.Emulation.Consoles.Nintendo
 				}
 			};
 
-			public class Reg_2000
+			public sealed class Reg_2000
 			{
 				PPU ppu;
 				public Reg_2000(PPU ppu)