sub_of - subtract two integers, check for arithmetic overflow

       In the multiplication functions, a return value of 1 signals success and 0 failure. In add_of, sub_of and
       assign it's the other way around.

       If calculating a-b is possible without causing undefined behavior or an arithmetic overflow in C, and the
       result fits into the destination integer type, do dest=a-b and return 0.

       Otherwise, return 1.

       Note: This is a macro, so dest does not have to be a pointer.

       sub_of - subtract two integers, check for arithmetic overflow

add_of(3), assign(3), imult16(3), umult16(3), imult32(3), umult32(3), imult64(3), umult64(3)

                                                                                                       sub_of(3)

#include<libowfat/rangecheck.h>

       int sub_of(dest,a,b);