When the application sets SA_SIGINFO, the signal trampoline parameters
are different to follow POSIX.
libgcc/
* config/i386/gnu-unwind.h (x86_gnu_fallback_frame_state): Add the
posix siginfo case to struct handler_args. Detect between legacy
and siginfo from the second parameter, which is a small sigcode in
the legacy case, and a pointer in the siginfo case.