[patch/rfc] Add a sentinel frame

[Michael Elizabeth Chastain]

> Anyway, I've got an x86-64 gdb.  You wouldn't have some patches to fix 
> sware's expect would you?  Sware's expect doesn't appear to work :-(

Would it be feasible to try stock expect?  That's what I test with anyways.

  ftp://ftp2.sourceforge.net/pub/sourceforge/tcl/tcl8.4.1-src.tar.gz
  http://expect.nist.gov/src/expect-5.38.0.tar.gz
  ftp://ftp.gnu.org/dejagnu/dejagnu-1.4.3.tar.gz

Sware expect dates to 1998-06-15, but sware tcl and sware dejagnu are
actually almost identical to the latest released version.

If it's not feasible to do this just forget I said anything.

Michael C