ck_main: Allow specifying difficulty with /TEDLEVEL

In theory, you should be able to test different difficulty levels with /EASY,
/NORMAL, /HARD when using /TEDLEVEL. This previously wasn't implemented, so
it always defaulted to Normal.

Note that the _first_ argument present is used, overriding any later ones.
Many other Omnispeak arguments works the other way (later ones overriding
earlier ones), but this should match Keen.

Author: sulix

src/ck_main.c

@@ -199,13 +199,21 @@ void CK_DemoLoop()
 
 	if (us_tedLevel)
 	{
+		static const char *difficultyParms[] = {"easy", "normal", "hard", ""};
 		CK_NewGame();
 		CA_LoadAllSounds();
 		ck_gameState.currentLevel = us_tedLevelNumber;
 		ck_startingDifficulty = D_Normal;
 
-		// TODO: Support selecting difficulty via an extra command line
-		// argument ("easy", "normal", "hard")
+		for (int i = 1; i < us_argc; ++i)
+		{
+			int difficulty = US_CheckParm(us_argv[i], difficultyParms);
+			if (difficulty == -1)
+				continue;
+
+			ck_startingDifficulty = (CK_Difficulty)((int)D_Easy + difficulty);
+			break;
+		}
 
 		CK_GameLoop();
 		Quit(0); // run_ted