Improved and fixed the playback of alternative sound files

Added a new mode to play_sfall_sound script function.

artifacts/scripting/sfall function notes.txt

@@ -66,7 +66,7 @@ get/set_proto_data are used to manipulate the in memory copies of the .pro files
 
 the list_xxx functions can be used to loop over all items on a map. list_begin takes an argument telling sfall what you want to list. (Defined in sfall.h) It returns a list pointer, which you iterate through with list_next. Finally, when you've finished with the list use list_end on it. Not calling list_end will result in a memory leak. Alternatively, use list_as_array to get the whole list at once as a temp array variable, which can be looped over using len_array and which you don't need to remember to free afterwards.
 
-play_sfall_sound and stop_sfall_sound are used to play mp3/wav/wma files. The path given is relative to the Fallout folder. Specify loop as 1 to loop the file continuously, or 0 otherwise. If you don't wish to loop, play_sfall_sound returns 0. If you do loop, it returns an id which can be passed back to stop_sfall_sound when you want to stop the effect. All sounds effects will be stopped on game reload, looping or not. These functions do not require 'AllowDShowSound' to be set to 1 in ddraw.ini.
+play_sfall_sound and stop_sfall_sound are used to play mp3/wav/wma files. The path given is relative to the Fallout folder. Specify mode as 1 to loop the file continuously, 2 to replace the current background game music with playing the specified file in loop mode, or 0 to play the file once. If you don't wish to loop, play_sfall_sound returns 0. If you do loop, it returns an id which can be passed back to stop_sfall_sound when you want to stop the effect. All sounds effects will be stopped on game reload, looping or not. These functions do not require 'AllowDShowSound' to be set to 1 in ddraw.ini.
 
 arrays are created and manipulated with the xxx_array functions. An array must first be created with create_array or temp_array, specifying how many data elements the array can hold. You can store any of ints, floats and strings in an array, and can mix all 3 in a single array. The id returned by create/temp_array can then be used with the other array functions. Arrays are shared between all scripts. (i.e. you can call create_array from one script, and then use the returned id from another script.) They are also saved across savegames. You must remember to free any arrays you create with create_array when you are done with them, or you will leak memory. arrays created with temp_array will be automatically freed at the end of the frame. These functions are safe, in that supplying a bad id or trying to access out of range elements will not crash the script. create_array is the only function that returns a permanent array, all other functions which return arrays (string_split, list_as_array etc,) all return temp arrays. You can use fix_array to make a temp array permanent.
 

artifacts/scripting/sfall opcode list.txt

@@ -296,8 +296,8 @@
 
 0x8228 - int get_attack_type
 
-0x822b - int  play_sfall_sound(string file, bool loop)
-0x822c - void stop_sfall_sound(int id)
+0x822b - int  play_sfall_sound(string file, int mode)
+0x822c - void stop_sfall_sound(int soundID)
 
 0x8235 - array string_split(string string, string split)
 0x8237 - int   atoi(string string)