Get rid of references to Tcl 8.7: It won't be released.

Protect Tk_SetSizeHints(): If an extension is compiled with Tk 9.1 bu…

…t running on Tk 9.0, tkStubsPtr->tk_SetSizeHints is NULL. In that case, just do nothing.

testutils.tcl [pause]: more simplification

Fix tclUpdateObjProc field usage

Check the TK_ALREADY_DEAD flag before making a window become the key …

…window.

Remove more dead code

Rebase to 9.0

 Alphabetise message range checks. Simplify unneeded checks for NULL …

…values

Make setting of command prefix for -[xy]scrollcommand more efficient

updated changes.md for release