Add fnspec handling to ipa mode of ipa-modef.

gcc/:

	* attr-fnspec.h (attr_fnspec::get_str): New accessor
	* ipa-fnsummary.c (read_ipa_call_summary): Store also parm info
	for builtins.
	* ipa-modref.c (class fnspec_summary): New type.
	(class fnspec_summaries_t): New type.
	(modref_summary::modref_summary): Initialize writes_errno.
	(struct modref_summary_lto): Add writes_errno.
	(modref_summary_lto::modref_summary_lto): Initialize writes_errno.
	(modref_summary::dump): Check for NULL pointers.
	(modref_summary_lto::dump): Dump writes_errno.
	(collapse_loads): Move up in source file.
	(collapse_stores): New function.
	(process_fnspec): Handle also internal calls.
	(analyze_call): Likewise.
	(analyze_stmt): Store fnspec string if needed.
	(analyze_function): Initialize fnspec_sumarries.
	(modref_summaries_lto::duplicate): Copy writes_errno.
	(modref_write): Store writes_errno and fnspec summaries.
	(read_section): Read writes_errno and fnspec summaries.
	(modref_read): Initialize fnspec summaries.
	(update_signature): Fix formating.
	(compute_parm_map): Return true if sucessful.
	(get_parm_type): New function.
	(get_access_for_fnspec): New function.
	(propagate_unknown_call): New function.
	(modref_propagate_in_scc): Use it.
	(pass_ipa_modref::execute): Delete fnspec_summaries.
	(ipa_modref_c_finalize): Delete fnspec_summaries.
	* ipa-prop.c: Include attr-fnspec.h.
	(ipa_compute_jump_functions_for_bb):  Also compute jump functions
	for functions with fnspecs.
	(ipa_read_edge_info): Read jump functions for builtins.

gcc/testsuite/ChangeLog:

	* gcc.dg/ipa/modref-2.c: New test.
	* gcc.dg/lto/modref-2_0.c: New test.