[libcxxabi][PATCH] use return address register from CIE

[Joerg Sonnenberger]

On Thu, Apr 24, 2014 at 06:55:06PM -0700, Nick Kledzik wrote:
> I got a bug report that the unwinder is not using the
> return_address_register value in the CIE.  This patch fixes that.

I had this feature on my TODO list, thanks for doing it. One obvious
question is the size of the return register field. The highest value
used on the architectures I have supported in NetBSD is ARM with 128.
Any reason for not limitting it to uint8_t and putting it near the end
with the bool fields?

Joerg