Added DivisionOperatorFix option for signed integer division (#278)

* it changes the behavior of vanilla division operator to use signed
integer division. Before it used signed division for floats but
unsigned for integers.

Added a new "div" operator for unsigned integer division.
Moved mathematical script functions from ScriptUtils.hpp to new MathOps.
Added include guard to sfall.h and main.h in modders pack.

artifacts/scripting/headers/lib.math.h

@@ -10,10 +10,10 @@
 #define below(a, b)        (unsigned_comp(a, b) < 0)
 #define below_equal(a, b)  (unsigned_comp(a, b) <= 0)
 
-procedure unsigned_comp(variable a, variable b) begin
+// for sfall 4.2.3/3.8.23
+pure procedure unsigned_comp(variable a, variable b) begin
    if ((a bwxor b) == 0) then return 0; // a == b
-   if (b == 0) then return 1;
-   return 1 if (a / b) else -1;
+   return 1 if ((b == 0) orElse a div b) else -1;
 end
 
 #define MAX(x, y)    ((x > y) * x + (x <= y) * y)

artifacts/scripting/headers/sfall.h

@@ -1,3 +1,6 @@
+#ifndef SFALL_H
+#define SFALL_H
+
 //Recognised modes for set_shader_mode and get_game_mode
 #define WORLDMAP    (0x1)
 #define DIALOG      (0x4)
@@ -305,3 +308,5 @@
 #define unjam_lock(obj)                                 sfall_func1("unjam_lock", obj)
 #define unset_unique_id(obj)                            sfall_func2("set_unique_id", obj, -1)
 #define unwield_slot(critter, slot)                     sfall_func2("unwield_slot", critter, slot)
+
+#endif