Reverted the previous commit and added "obj_is_openable" function

* the previous commit conflicts with BIS document.

artifacts/scripting/headers/sfall.h

@@ -365,6 +365,7 @@
 #define message_box(text)                                       sfall_func1("message_box", text)
 #define metarule_exist(metaruleName)                            sfall_func1("metarule_exist", metaruleName)
 #define npc_engine_level_up(toggle)                             sfall_func1("npc_engine_level_up", toggle)
+#define obj_is_openable(obj)                                    sfall_func1("obj_is_openable", obj)
 #define obj_under_cursor(onlyCritter, includeDude)              sfall_func2("obj_under_cursor", onlyCritter, includeDude)
 #define objects_in_radius(tile, radius, elev, type)             sfall_func4("objects_in_radius", tile, radius, elev, type)
 #define outlined_object                                         sfall_func0("outlined_object")

artifacts/scripting/sfall function notes.md

@@ -1048,6 +1048,11 @@ sfall_funcX metarule functions
 - Passing an empty string ("") to the `name` argument or omitting it will allow the game to get the name for the object from pro_*.msg files
 - __NOTE:__ this function is intended for use in normal game scripts and overrides the name only once for the same object until reset
 
+----
+#### obj_is_openable
+`bool sfall_func1("obj_is_openable", object obj)`
+- Returns True if the object is openable (i.e. has an opening/closing animation)
+
 
 ****
 _See other documentation files (arrays.md, hookscripts.md) for related functions reference._