new pce cores - add some button name overrides, and support mnemonics

src/BizHawk.Client.Common/movie/bk2/Bk2MnemonicLookup.cs

@@ -445,6 +445,17 @@ namespace BizHawk.Client.Common
 				["V"] = '5',
 				["VI"] = '6',
 			},
+			["PCE"] = new Dictionary<string, char>
+			{
+				["I"] = '1',
+				["II"] = '2',
+				["III"] = '3',
+				["IV"] = '4',
+				["V"] = '5',
+				["VI"] = '6',
+				["Mode: Set 2-button"] = 'm',
+				["Mode: Set 6-button"] = 'M'
+			},
 			["NDS"] = new Dictionary<string, char>
 			{
 				["LidOpen"] = 'o',

src/BizHawk.Emulation.Cores/Consoles/NEC/PCE/HyperNyma.cs

@@ -52,7 +52,12 @@ namespace BizHawk.Emulation.Cores.Consoles.NEC.PCE
 
 		protected override IDictionary<string, string> ButtonNameOverrides { get; } = new Dictionary<string, string>
 		{
-			{ "RIGHT →", "Right up my arse" },
+			["UP ↑"] = "Up",
+			["DOWN ↓"] = "Down",
+			["LEFT ←"] = "Left",
+			["RIGHT →"] = "Right",
+			["SELECT"] = "Select",
+			["RUN"] = "Run"
 		};
 
 		// pce always has two layers, sgx always has 4, and mednafen knows this

src/BizHawk.Emulation.Cores/Consoles/NEC/PCE/TurboNyma.cs

@@ -61,7 +61,12 @@ namespace BizHawk.Emulation.Cores.Consoles.NEC.PCE
 
 		protected override IDictionary<string, string> ButtonNameOverrides { get; } = new Dictionary<string, string>
 		{
-			{ "RIGHT →", "Right up my arse" },
+			["UP ↑"] = "Up",
+			["DOWN ↓"] = "Down",
+			["LEFT ←"] = "Left",
+			["RIGHT →"] = "Right",
+			["SELECT"] = "Select",
+			["RUN"] = "Run"
 		};
 
 		// pce always has two layers, sgx always has 4, and mednafen knows this