Add locale tool to generate "rollup" UTF-8 src file

Add locale tool to generate "rollup" UTF-8 src file

The first version of the "common" UTF-8 file was hand-assembled by myself.
This is obviously prone to error and is very hard to maintain (the
previous incarnation was never maintained; not once after it was added).

To address these issues, create a new tool (using cldr2def as inspiration)
to create a composite UTF-8 source files using all available POSIX input
from CLDR.  What can't be generated still comes from a manual fragment
that is added to the common source file at the end.

This allows periodic maintenance when CLDR issues new releases.  We are
converging on using this composite (aka "rollup") file for all UTF-8
locales.