For the header only version, the global variable default_random no more exist => we need to replace all occurences of default_random by a call to the global function get_default_random().
As usual, no modification for the non header only version.
There is const static variable, transformed into a static variable of a global function. This is not a problem since this is only used in debug mode to test the rounding mode at the end of the program. Testing it several times is ok.