Add a test tool that will allow comparison between releases to identify regressions

[jeking3]

In general, Boost.Format is a stable and long-lived component and used by many consumers. Changes to the behavior of Boost.Format could cause widespread issues. A mechanism is needed that will allow comparison of one edition of Boost.Format to another to ensure there haven't been any regressions.

Proposal

Create a matrix tester that will attempt to generate every possible format syntax string expression, and test against a variety of inputs appropriate to that type, and output the results to a text file which will be considered the results file. The results file format is:

# glibc.version = n
{format specification}<tab>OK |ERR<tab>string result or exception message
...

The tool will also allow for results to be generated against the platform's snprintf call, so that boost::format and snprintf on the same inputs and format specifications can be compared.