Load an unlimited amount of sounds

This commit allows the usage of new "extra" sounds in levels for use in
custom level scripting. Including `squid.ogg` inside of your sounds
folder will now allow for the usage of the command `playef(squid)`.
Additionally, you can play built-in sounds by name this way too,
instead of having to memorize the id (`playef(rescue)`).

However, you CANNOT play extra sounds through using their numerical
IDs, since those can shift around depending on the filesystem (or if
someone adds a new sound). Playing an extra sound by ID will NOT play
the sound.

This is another attempt at #902, being loosely based off of that PR.

Co-authored-by: Fussmatte <doormattion@gmail.com>

desktop_version/src/Script.cpp

@@ -447,7 +447,14 @@ void scriptclass::run(void)
             }
             if (words[0] == "playef")
             {
-                music.playef(ss_toi(words[1]));
+                if (music.soundidexists(words[1].c_str()))
+                {
+                    music.playefid(words[1].c_str());
+                }
+                else if (!music.soundisextra(ss_toi(words[1])))
+                {
+                    music.playef(ss_toi(words[1]));
+                }
             }
             if (words[0] == "play")
             {