Patch: Use _Unwind_GetIPInfo in stacktrace.cc

[Bryce McKinlay]

Steve Ellcey wrote:
> This makes me wonder if the libstdc++ check would work for libjava.  If
> it would I will create a C++ patch and try to get it checked in but if it
> won't work for java because java doesn't want to try linking anything
> during configuration then how do we check for __Unwind_GetIPInfo?
>   

We can make this check run conditionally, ie only on native builds. 
There are already a lot of checks conditionalized in this way in 
libjava's configure.ac. For a cross, its probably safe to assume we are 
using the real libgcc and thus do have it.

Bryce