[PATCH] libdw: Enable building with -Og.

[Mark Wielaard]

On Fri, 2018-11-23 at 21:08 +0100, Mark Wielaard wrote:
> When building with -Og gcc is unable to see that __libdw_dieabbrev ()
> will initialize what the second argument points to when no error
> occurs
> as called by dwarf_child and dwarf_getattrs. Causing an possibly
> uninitialized error. Just initialize readp/die_addr to NULL, which is
> the value we would return if an error occurs anyway.
> 
> https://sourceware.org/bugzilla/show_bug.cgi?id=23914

Pushed to master.