libunwind related patch from David Mosberger
* unwind-libunwind.c (_Unwind_SetGR): Clear the NaT bit as
required by C++ ABI for Itanium.
* config/t-libunwind (LIB2ADDEH): Remove unwind-libunwind.c.
* config/t-libunwind-no-eh: New file.
* configure.in: Check libunwind for _Unwind_Resume() and if it's
present, set libunwind_has_eh_support to "yes".
* configure: Regenerate.
* config.gcc (ia64*-*-linux*): If $libunwind_has_eh_support is
set to yes, use t-libunwind, otherwise, use t-libunwind-no-eh.

From-SVN: r74548