[lto][patch] Fix linking error

[Rafael Espindola]

The attached patch fixes the include testcase. The problem was that
cc1plus was writing function decls to disk that were only reachable
via the DECL_INITIAL of a vtable. It was doing so even if the vtable
had a home in another file and the vtable VAR_DECL was DECL_EXTERNAL.
Since the function decl was not really used, there was no cgraph node
for it.

In wpa we assume that if a decl has a node, then the prevailing decl
also has. This was false if the file described  above (with a decl but
no cgraph node for it) was linked with a file that actually used the
function and therefore had both a function decl and a node.

One option would be to make wpa handle that case, but it is much
easier to just ovoid writing decls that are not used.

Bootstrapped and regression tested.

2009-03-11  Rafael Avila de Espindola  <espindola@google.com>

	* g++.dg/lto/20090311_0.C: New.
	* g++.dg/lto/20090311_1.C: New.

2009-03-11  Rafael Avila de Espindola  <espindola@google.com>

	* tree.c (free_lang_data_in_decl): Free DECL_INITIAL of DECL_EXTERNAL
	VAR_DECLs.

Cheers,
-- 
Rafael Avila de Espindola

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