[PATCH] libdw: Add new dwarf_cu_info function.

[Mark Wielaard]

On Sun, 2018-05-20 at 15:21 +0200, Mark Wielaard wrote:
> This allows getting a (split) subdie lazily, only when needed.
> All arguments to dwarf_get_units are optional. When not given
> then unit DIE and sub DIE are not looked up. This new function
> allows them to be looked up when not immediately retrieved with
> dwarf_get_units, or for a Dwarf_CU gotten through some other way.
> 
> Add a new testcase to make sure the results of calling dwarf_cu_info
> and dwarf_get_units are consistent.

Pushed to master.