Add "displayname" keyvalue for custom monster names.

src/dlls/islave.cpp

@@ -434,6 +434,11 @@ void CMISlave :: Spawn()
 
 	MonsterInit();
 	pev->classname = MAKE_STRING( "monster_alien_slave" );
+	if ( strlen( STRING( m_szMonsterName ) ) == 0 )
+	{
+		// default name
+		m_szMonsterName = MAKE_STRING( "Alien Slave" );
+	}
 }
 
 //=========================================================