void SetSetupSetting(str DirectiveName, str Value)
Modifies or generates a [Setup] section directive using the directive name (first parameter) and its value (second parameter).
If there is no [Setup] section in current preprocessor output (it may happen that the function is called before that section in a script), its header (as well as the directive itself) is generated by this function.
This function shouldn't be called when ISPP is in insert mode (that is, after the insert directive).