libbacktrace: add DWARF 5 support

	* dwarf.c (struct attr): Add val field.
	(enum attr_val_encoding): Add ATTR_VAL_ADDDRESS_INDEX,
	ATTR_VAL_STRING_INDEX, ATTR_VAL_RNGLISTS_INDEX.
	(struct line_header): Add addrsize field.
	(struct line_header_format): Define.
	(struct unit): Add str_offsets_base, addr_base, and rnglists_base
	fields.
	(read_uint24): New static function.
	(read_attribute): Add implicit_val parameter.  Replace dwarf_str
	and dwarf_str_size parameters with dwarf_sections parameter.  Add
	support for new DWARF 5 forms.  Change all callers.
	(resolve_string): New static function.
	(resolve_addr_index): Likewise.
	(read_abbrevs): Support DW_FORM_implicit_const.
	(struct pcrange): Add lowpc_is_addr_index, highpc_is_addr_Index,
	and ranges_is_index fields.
	(update_pcrange): Support DWARF 5 encodings.
	(add_high_low_range): New static function, split out of
	add_ranges.
	(add_ranges_from_ranges): Likewise.
	(add_ranges_from_rnglists): New static function.
	(add_ranges): Just call new helper functions.
	(find_address_ranges): Use resolve_string for strings, after
	reading all attributes.  Handle new DWARF 5 attributes.
	(build_address_map): Support DWARF 5 compilation units.
	(read_v2_paths): New static function, split out of
	read_line_header.
	(read_lnct): New static	function.
	(read_line_header_format_entries): Likewise.
	(read_line_header): Add ddata parameter.  Support DWARF 5 line
	headers.  Call new helper functions.  Change all callers.
	(read_line_program): Use addrsize from line program header.  Don't
	special case directory index 0 for DWARF 5.
	(read_referenced_name): Use resolve_string.
	(read_function_entry): Handle DWARF 5 encodings.  Use
	resolve_string.
	* internal.h (enum dwarf_section): Add DEBUG_ADDR,
	DEBUG_STR_OFFSETS, DEBUG_LINE_STR, DEBUG_RNGLISTS.
	* elf.c (dwarf_section_names): Add new section names.
	* pecoff.c (dwarf_section_names): Likewise.
	* xcoff.c (xcoff_add): Clear dwarf_sections before setting
	fields.
	* configure.ac: Define HAVE_DWARF5 automake conditional.
	* Makefile.am (dwarf5_SOURCES): New variable if HAVE_DWARF5.
	(dwarf5_CFLAGS, dwarf5_LDADD): Likewise.
	(dwarf5_alloc_SOURCES, dwarf5_alloc_CFLAGS): Likewise.
	(dwarf5_alloc_LDADD): Likewise.
	(BUILDTESTS): Add dwarf5 tests if HAVE_DWARF5.
	(CLEANFILES, clean-local): Define.

From-SVN: r279380