[Mono-list] System private libraries

[Derek Holden]

I've started working through the relationships of all the Formattable /
IFormatProvider / FormatInfo classes that make up the ToString and Parse
methods in all of the core data types. There is going to a lot of similar
code blocks and argument validity checking across the board.

Do we have any System.Private type of namespace where some of these shared
methods could go? Should I just add them as protected methods in one of the
interface classes, make some separate class for handling this and bundle it
alongside, or just cut and paste in every place?