[PATCH v2] libstdc++: Make certain exceptions transaction_safe.

[Dominique d'Humières]

> Addressed these, fixed a problem with using GLIBCXX_WEAK_DEFINITION
> (which is only set on Darwin despite the generic-sounding name -- so
> just use __attribute__((weak)) directly), and also updated
> testsuite_abi.cc so that it knows about CXXABI_1.3.10.
>
> Approved by Jonathan Wakely.  Committed as r232454.
This breaks bootstrap on darwin, see https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69310.

TIA

Dominique