Auto-generate file header comments in Unicode mapping files.

Some of the Unicode/*.map files had identification comments added to them,
evidently by hand.  Others did not.  Modify the generating scripts to
produce these comments automatically, and update the generated files that
lacked them.

This is just minor cleanup as a by-product of trying to verify that the
*.map files can indeed be reproduced from authoritative data.  There are a
depressingly large number that fail to reproduce from the claimed sources.
I have not touched those in this commit, except for the JIS 2004-related
files which required only a single comment update to match.

Since this only affects comments, no need to consider a back-patch.