For every integer type S, S'Integer_Value denotes a
function with the following spec:
function S'Integer_Value (Arg : Universal_Fixed)
return S;
The value returned is the integer value V, such that
Arg = V * T'Small
where T is the type of Arg.
The effect is thus similar to first doing an unchecked conversion from
the fixed-point type to its corresponding implementation type, and then
converting the result to the target integer type. The difference is
that there are full range checks, to ensure that the result is in range.
This attribute is primarily intended for use in implementation of the
standard input-output functions for fixed-point values.