[RFA] testsuite/gdb.c++/ref-types.exp: use runto

[Michael Elizabeth Chastain]

Michael Snyder asks:
> When are we going to stop doing that???

The new C++ ABI has a public multi-vendor specification:

  http://reality.sgi.com/dehnert_engr/cxx/cxx-summary.html

The existence of a spec is a very good thing for gdb.

Michael