Basic number definitions and coefficient rings and fields.

The definition of floating-point numbers is such that it is independent
of the pre-defined type "float".

1. Floating-point and complex numbers

     float            Floating_Point_Numbers
     mathfun          Mathematical_Functions
     complex          Complex_Numbers
     complex_io       Complex_Numbers_io
     numbers_io       Numbers_io

2. Instantiation packages to define coefficient rings

     nat_inst         Natural_Instantiation_Parameters
     int_inst         Integer_Instantiation_Parameters
     flt_inst         Float_Instantiation_Parameters
     cmp_inst         Complex_Instantiation_Parameters

3. Random number generators

     random           Random_Number_Generators

4. Conversions: strings to numbers.

     strnum           Strings_to_Natural_Numbers
