[TCLCORE] preparation for 8.4.12 release

[Donald G P. <dg...@ni...>]

I've bumped the version numbers on core-8-4-branch, and added "8.4.12"
entries in the "Groups" of the Bug Trackers, and updated the changes
files.

Intent is to get Tcl/Tk 8.4.12 released on November 30.  That's more
than 5 months since the 8.4.11 release.

Now's the time for vigorous testing to be sure that release is worthy.
Thanks.

| Don Porter          Mathematical and Computational Sciences Division |
| don...@ni...             Information Technology Laboratory |
| http://math.nist.gov/~DPorter/                                  NIST |
|______________________________________________________________________|