DWARF-5: .debug_names index consumer

DWARF-5: .debug_names index consumer

Some testcases needed to be updated as they were missing
.debug_aranges.  While that does not matter for no-index (as GDB
builds the mapping internally during dwarf2_build_psymtabs_hard) and
neither for .gdb_index (as GDB uses that internally built mapping
which it stores into .gdb_index) it does matter for .debug_names as
that simply assumes existing .debug_aranges from GCC.

gdb/ChangeLog:
2017-12-08  Jan Kratochvil  <jan.kratochvil@redhat.com>
	    Pedro Alves  <palves@redhat.com>

	* defs.h (elf_sym_fns_debug_names): New declaration.
	* dwarf2read.c: Include "hash_enum.h".
	(mapped_debug_names): New.
	(struct dwarf2_per_objfile): Add debug_names, debug_aranges and
	debug_names_table.
	(dwarf2_elf_names): Add ".debug_names" and ".debug_aranges".
	(struct dwz_file): Add debug_names.
	(dwarf2_per_objfile::locate_sections): Handle debug_names and
	debug_aranges.
	(locate_dwz_sections): Handle debug_names.
	(create_signatured_type_table_from_debug_names)
	(create_addrmap_from_aranges): New.
	(dwarf2_read_index): Update function comment.
	(dwarf5_augmentation): Moved up.
	(read_debug_names_from_section, create_cus_from_debug_names_list)
	(create_cus_from_debug_names, dwarf2_read_debug_names): New.
	(dwarf5_djb_hash): Moved up.
	(dw2_debug_names_iterator): New.
	(read_indirect_string_at_offset): New declaration.
	(mapped_debug_names::namei_to_name)
	(dw2_debug_names_iterator::find_vec_in_debug_names)
	(dw2_debug_names_iterator::next, dw2_debug_names_lookup_symbol)
	(dw2_debug_names_dump, dw2_debug_names_expand_symtabs_for_function)
	(dw2_debug_names_expand_symtabs_matching, dwarf2_debug_names_functions):
	New.
	(dwarf2_initialize_objfile): Return also elf_sym_fns_debug_names.
	(debug_names::djb_hash): Rename it to dwarf5_djb_hash.
	(debug_names::build): Update djb_hash caller.
	(write_debug_names): Move out and rename augmentation to
	dwarf5_augmentation.
	* elfread.c (elf_sym_fns_debug_names): New.
	* psymtab.h (dwarf2_debug_names_functions): New declaration.
	* symfile.h (struct dwarf2_debug_sections): Add debug_names and
	debug_aranges.
	* xcoffread.c (dwarf2_xcoff_names): Add debug_names and debug_aranges.

gdb/testsuite/ChangeLog:
2017-12-08  Jan Kratochvil  <jan.kratochvil@redhat.com>
	    Pedro Alves  <palves@redhat.com>

	* gdb.base/maint.exp (check for .gdb_index): Check also for
	.debug_names.
	* gdb.dlang/watch-loc.c (.debug_aranges): New.
	* gdb.dwarf2/dw2-case-insensitive-debug.S: Likewise.
	* gdb.dwarf2/gdb-index.exp (check if index present, .gdb_index used)
	(.gdb_index used after symbol reloading): Support also .debug_names.
	* gdb.mi/dw2-ref-missing-frame-func.c (.debug_aranges): New.