re PR pch/51722 (Options "-g3" or "-ggdb3" or "-g3 -gdwarf-2" and other...

re PR pch/51722 (Options "-g3" or "-ggdb3" or "-g3 -gdwarf-2" and other "-g..level3" - internal compiler error)

	PR pch/51722
	* dwarf2out.c (dwarf2out_start_source_file, dwarf2out_define,
	dwarf2out_undef): Allocate e.info using ggc_strdup instead
	of xstrdup.
	(output_macinfo_op): Don't ggc_strdup fd->filename.
	(optimize_macinfo_range): Allocate grp_name using XALLOCAVEC,
	then ggc_strdup it.  Don't free inc->info or cur->info.
	(output_macinfo): Don't free ref->info or file->info.

From-SVN: r182845