* symtab.c (symtab_node::equal_address_to): New function.
	* cgraph.h (symtab_node::equal_address_to): Declare.
	* fold-const.c (fold_comparison, fold_binary_loc): Use it.

	* c-family/c-common.c: Refuse weaks for symbols that can not change
	visibility.

	* gcc.dg/addr_equal-1.c: New testcase.

From-SVN: r218462