Binutils support for split-dwarf and dwarf-5

	* dwarf.c (fetch_indexed_string): Added new parameter
	str_offsets_base to calculate the string offset.
	(read_and_display_attr_value): Read DW_AT_str_offsets_base
	attribute.
	(process_debug_info): While allocating memory and initializing
	debug_information, do it for do_debug_info also, if its true.
	(load_separate_debug_files): Load .debug_str_offsets if exists.
	* dwarf.h (struct debug_info): Add str_offsets_base field.