Remove ALL_OBJFILE_PSYMTABS

This removes the ALL_OBJFILE_PSYMTABS macro, replacing its uses with
ranged for loops.

gdb/ChangeLog
2019-01-09  Tom Tromey  <tom@tromey.com>

	* dbxread.c (dbx_end_psymtab): Use objfile_psymtabs.
	* mdebugread.c (parse_partial_symbols): Use objfile_psymtabs.
	* psymtab.c (ALL_OBJFILE_PSYMTABS_REQUIRED): Remove.
	(psym_map_symtabs_matching_filename, find_pc_sect_psymtab)
	(psym_lookup_symbol, psym_find_last_source_symtab)
	(psym_forget_cached_source_info, psym_print_stats)
	(psym_expand_symtabs_for_function, psym_expand_all_symtabs)
	(psym_expand_symtabs_with_fullname, psym_map_symbol_filenames)
	(psym_map_matching_symbols, psym_expand_symtabs_matching)
	(psym_find_compunit_symtab_by_address)
	(maintenance_print_psymbols, maintenance_info_psymtabs)
	(maintenance_check_psymtabs): Use ranged for.
	* psymtab.h (class objfile_psymtabs): New.
	(require_partial_symbols): Return objfile_psymtabs.
	* psympriv.h (ALL_OBJFILE_PSYMTABS): Remove.