Add comments to Gambatte's `ITraceable` impl.

src/BizHawk.Emulation.Cores/Consoles/Nintendo/Gameboy/Gambatte.ITraceable.cs

@@ -44,7 +44,7 @@ namespace BizHawk.Emulation.Cores.Nintendo.Gameboy
 				registerInfo: string.Format(
 					"A:{3:x2} F:{8:x2} B:{4:x2} C:{5:x2} D:{6:x2} E:{7:x2} H:{9:x2} L:{10:x2} LY:{13:x2} SP:{2:x2} {11} Cy:{0}",
 					(ulong)s[0] + _cycleCount,
-					s[1] & 0xffff,
+					s[1] & 0xffff, // unused (this is the PC)
 					s[2] & 0xffff,
 					s[3] & 0xff,
 					s[4] & 0xff,
@@ -55,7 +55,7 @@ namespace BizHawk.Emulation.Cores.Nintendo.Gameboy
 					s[9] & 0xff,
 					s[10] & 0xff,
 					s[11] != 0 ? "prefetched" : "",
-					s[12] & 0xffffff,
+					s[12] & 0xffffff, // unused (this is the opcode)
 					s[13] & 0xff)));
 		}
 	}