[lto] PATCH: Make global function/variable references work

[Kenneth Zadeck]

Mark Mitchell wrote:
> This patch wires up bits to write out and read in references to global
> variables and global functions from the bodies of functions.
>
> I was hoping this small program:
>
>   extern int i;
>
>   void f(int j) {
>     f(i);
>   }
>
> could be round-tripped with this patch, but it causes the
> function-body reader to crash.  
>
> Kenny, will you have time to work on that?  
>
>   
I will try to look at it this weekend. 

kenny
> Also, you've got some debugging output printing from
> lto-function-out.c; that needs to be turned off before we can do
> automated testing.  Would you please conditionalize this on some macro
> that you can turn on/off in lto-function-out.c in your own tree for
> debugging?
>
> Committed to LTO branch.
>