re PR ipa/58329 (ld: Invalid symbol type for plabel (.libs/libstdc++.lax/libc++11convenience.a/system_error.o, std::error_category::default_error_condition(int) const [clone .localalias.9]).)


	PR middle-end/58329
	* ipa-devirt.c (ipa_devirt): Be ready for symtab_nonoverwritable_alias
	to return NULL.
	* ipa.c (function_and_variable_visibility): Likewise.
	* ipa-profile.c (ipa_profile): Likewise.

From-SVN: r202658