[libunwind] C++ and libunwind

[Todd L Miller]

        In include/libunwind-dynamic.h, I've had to alter the macro
_U_dyn_op, because it doesn't compile with g++ (3.3.3):

#define _U_dyn_op(_t, _q, _w, _r, _v)       \
    ((unw_dyn_op_t) {           \
      (_t),             \
      (_q),             \
      (_r),             \
      (_w),             \
      (_v)              \
    })

The current macro seems to use C99-style initializers, which apparently
don't play nicely with C++.  Would it be a problem to change this for
the next release?

- Todd Miller