Add support for Military Conflict: Vietnam (#1887)

plugins/include/halflife.inc

@@ -90,7 +90,8 @@ enum EngineVersion
 	Engine_Contagion,           /**< Contagion */
 	Engine_BlackMesa,           /**< Black Mesa Multiplayer */
 	Engine_DOI,                 /**< Day of Infamy */
-	ENGINE_PVKII                /**< Pirates, Vikings, and Knights II */
+	Engine_PVKII = 26,          /**< Pirates, Vikings, and Knights II */
+	Engine_MCV,                 /**< Military Conflict: Vietnam */
 };
 
 enum FindMapResult

plugins/nextmap.sp

@@ -67,7 +67,8 @@ public APLRes AskPluginLoad2(Handle myself, bool late, char[] error, int err_max
 			|| StrEqual(game, "swarm", false)
 			|| StrEqual(game, "reactivedrop", false)
 			|| engine == Engine_Insurgency
-			|| engine == Engine_DOI)
+			|| engine == Engine_DOI
+			|| engine == Engine_MCV)
 	{
 		strcopy(error, err_max, "Nextmap is incompatible with this game");
 		return APLRes_SilentFailure;