I just went through a correct solution for:
	https://sourceforge.net/support/tracker.php?aid=1599877
and found that we weren't doing bounds checking with menu underlines.  It is
important to note that Tcl_UtfAtIndex does *not* do any bounds checking.  It
will gleefully run off the end of the valid string range.  Callers should make
sure to do correct bounding on the index that they pass in.

A quick grep reveals that its used in several places in Tk (and like the above
bug, probably needed in several places more).  I see already that tkUnixMenu.c
has the same unbounded index bug.

This is just a reminder to watch how you make use of that API
(Tcl_UniCharAtIndex is the same, as are a few other Tcl_Utf* helper routines
that expect you to know your bounds).

  Jeff Hobbs, The Tcl Guy, http://www.ActiveState.com/