PATCH: Factor __aeabi_atexit into its own object file

[Paolo Carlini]

Hi Mark,

>===================================================================
>--- libstdc++-v3/libsupc++/cxxabi.h	(revision 170155)
>+++ libstdc++-v3/libsupc++/cxxabi.h	(working copy)
>@@ -136,7 +136,7 @@ namespace __cxxabiv1
> 
>   // DSO destruction.
>   int
>-  __cxa_atexit(void (*)(void*), void*, void*);
>+  __cxa_atexit(void (*)(void*), void*, void*) throw ();
>
because of this change, abi/header_cxxabi.c is now failing. I'm not sure 
to remember the whole story, but certainly the header isn't C++-only, as 
the various #ifdef __cplusplus clearly show...

Paolo.