[PATCH][Revisedx2] Fix PR libitm/55693

[Jack Howarth <howarth at bromo dot med dot uc dot edu>]

   The attached patch eliminates, PR55693, the failure of the libitm.c++/eh-1.C execution test on
darwin10 and later. With the introduction of c++ weak-symbol coalescing in Mac OS X 10.6, dyld no
longer looks up weak symbols that reside in object files rather than shared libraries. This prevents
the weak symbols for the dummy functions in libgcc/config/darwin-crt-tm.c from being replaced
by those in the libstdc++ shared library. It appears that these dummy functions are not actually
required. Thus the hack for adding dummy symbols to libgcc/config/darwin-crt-tm.c is reverted.
Also, the previous hack of not declaring the dummy symbols in libitm/alloc_cpp.cc and libitm/eh_cpp.cc
on darwin is reverted as this produces undefined symbols for the combination of darwin10 with Xcode 4.2
(where HAVE_ELF_STYLE_WEAKREF is undefined). Bootstrap and regression tested on powerpc-apple-darwin9 
with Xcode 3.1.4, x86_64-apple-darwin10 with Xcode 4.2 as well as for x86_64-apple-darwin12 with
Xcode 4.6.
            Okay for gcc trunk after testing on intel darwin9?
                                Jack

Attachment: PR55693_v3.diff
Description: Text document