ipa.c (cgraph_externally_visible_p): Handle externally visible and preserve flags before trying to guess on visibility.

	* ipa.c (cgraph_externally_visible_p): Handle externally visible and
	preserve flags before trying to guess on visibility.
	(varpool_externally_visible_p): New function.
	(function_and_variable_visibility): Use it.

From-SVN: r165669