[TCLCORE] Commit block to tcl/tk-core-8-6-branch and main branch on TCL for non documentation and serious bug fix changes

[Harald O. <har...@el...>]

Dear TCL/Tk team,
we are approaching TCL/Tk 9.0.0 and TCL/Tk 8.6.15 releases.

Please keep any new features in own branches and please only merge 
considerable documentation and bug fixes to the main and core-8-6-branches.

Thank you for your cooperation,
Harald