Remove ALL_OBJFILE_FILETABS

Remove ALL_OBJFILE_FILETABS

This removes ALL_OBJFILE_FILETABS, replacing its uses with ranged for
loops.

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

	* symmisc.c (print_objfile_statistics, dump_objfile)
	(maintenance_print_symbols): Use compunit_filetabs.
	* source.c (forget_cached_source_info_for_objfile): Use
	compunit_filetabs.
	* objfiles.h (ALL_OBJFILE_FILETABS): Remove.
	(ALL_FILETABS): Use compunit_filetabs.
	* objfiles.c (objfile_relocate1): Use compunit_filetabs.
	* coffread.c (coff_symtab_read): Use compunit_filetabs.