re PR middle-end/41573 (segfault in trunk related to strings)

	PR middle-end/41573
	* builtins.c (fold_builtin_isascii): Use fold_build2.
	(fold_builtin_isdigit): Ditto.
	* except.c (duplicate_eh_regions_1): Tolerate NULL labels.
	* tree-cfg.c (struct rus_data, remove_useless_stmts_warn_notreached,
	remove_useless_stmts_cond, remove_useless_stmts_tf,
	remove_useless_stmts_tc, remove_useless_stmts_bind,
	remove_useless_stmts_goto, remove_useless_stmts_label,
	remove_useless_stmts_1, remove_useless_stmts,
	pass_remove_useless_stmts): Remove.
	* tree-pass.h (pass_remove_useless_stmts): Don't declare.
	* passes.c (init_optimization_passes): Don't add
	pass_remove_useless_stmts.
	* tree-eh.c (lower_eh_constructs_2): Handle empty cleanups.
	* tree.c (free_lang_data_in_decl): Don't clear DECL_INITIAL of
	static constants.
	* lto-symtab.c (lto_symtab_register_decl): Accepts DECL_INITIAL
	for static constants.
	* lto-streamer-out.c (output_gimple_stmt): Handle GIMPLE_NOP.
	* lto-streamer-in.c (input_gimple_stmt): Handle GIMPLE_NOP.

testsuite/
	* gcc.dg/tree-ssa/foldstring-1.c: Use fre dump.
	* gcc.dg/tree-ssa/useless-1.c: Use gimple dump.
	* gcc.dg/pr41573.c: New test.

From-SVN: r152563