Refined criteria for choosing custom sound effects

Previously, any number would be interpreted as a stock sound effect ID,
causing the side effect of being able to call custom sound effects using
numbers over 27 (which is unreliable).

Now only numbers that correspond to a stock sound effect ID will be
considered (leading zeroes work as well), and everything else will be
interpreted as a custom sound effect file name.

desktop_version/src/Music.cpp

@@ -614,6 +614,8 @@ musicclass::musicclass(void)
     quick_fade = true;
 
     usingmmmmmm = false;
+
+    stockSoundTracks = 0;
 }
 
 void musicclass::init(void)
@@ -659,6 +661,8 @@ void musicclass::init(void)
     soundTracks.push_back(SoundTrack( "sounds/newrecord.wav" ));
     soundTracks.push_back(SoundTrack( "sounds/trophy.wav" ));
     soundTracks.push_back(SoundTrack( "sounds/rescue.wav" ));
+
+    stockSoundTracks = soundTracks.size();
 
     //Here's where we find all the custom sounds in a level's assets folder
     EnumHandle handle = {};

desktop_version/src/Music.h

@@ -65,6 +65,8 @@ class musicclass
     bool mmmmmm;
     bool usingmmmmmm;
 
+    int stockSoundTracks;
+
     binaryBlob pppppp_blob;
     binaryBlob mmmmmm_blob;
     int num_pppppp_tracks;

desktop_version/src/Script.cpp

@@ -355,13 +355,13 @@ void scriptclass::run(void)
             }
             if (words[0] == "playef")
             {
-                if (words[1] != "0" && ss_toi(words[1]) == 0)
+                if (is_number(words[1].c_str()) && ss_toi(words[1]) >= 0 && ss_toi(words[1]) < music.stockSoundTracks)
                 {
-                    music.playef_name(raw_words[1]);
+                    music.playef(ss_toi(words[1]));
                 }
                 else
                 {
-                    music.playef(ss_toi(words[1]));
+                    music.playef_name(raw_words[1]);
                 }
             }
             if (words[0] == "play")