* cgraph.c (cgraph_function_body_availability): Do not check cgrpah flags.
	* cgraph.h (symtab_for_node_and_aliases, symtab_nonoverwritable_alias,
	symtab_node_availability): Declare.
	* ipa.c (can_replace_by_local_alias): New.
	(function_and_variable_visibility): Use it.
	* symtab.c (symtab_for_node_and_aliases, symtab_nonoverwritable_alias_1,
	symtab_nonoverwritable_alias): New.

Co-Authored-By: Martin Liska <marxin.liska@gmail.com>

From-SVN: r201439