This removes the objfile_compunits range adapter in favor of using a
method on objfile.

2019-01-15  Tom Tromey  <tom@tromey.com>

	* symtab.c (lookup_objfile_from_block)
	(lookup_symbol_in_objfile_symtabs)
	(basic_lookup_transparent_type_1, find_pc_sect_compunit_symtab)
	(find_line_symtab, info_sources_command)
	(default_collect_symbol_completion_matches_break_on)
	(make_source_files_completion_list): Update.
	* symmisc.c (print_objfile_statistics, dump_objfile)
	(maintenance_print_symbols, maintenance_info_symtabs)
	(maintenance_check_symtabs, maintenance_info_line_tables):
	Update.
	* source.c (select_source_symtab)
	(forget_cached_source_info_for_objfile): Update.
	* objfiles.h (class objfile_compunits): Remove.
	(struct objfile) <compunits_range>: New typedef.
	(compunits): New method.
	* objfiles.c (objfile_relocate1): Update.
	* mi/mi-cmd-file.c (mi_cmd_file_list_exec_source_files): Update.
	* maint.c (count_symtabs_and_blocks): Update.
	* linespec.c (iterate_over_all_matching_symtabs): Update.
	* cp-support.c (add_symbol_overload_list_qualified): Update.
	* coffread.c (coff_symtab_read): Update.
	* ada-lang.c (add_nonlocal_symbols)
	(ada_collect_symbol_completion_matches)
	(ada_add_global_exceptions): Update.