Make minimal symbol range adapter a method on objfile

Make minimal symbol range adapter a method on objfile

This removes class objfile_msymbols in favor of a method on the
objfile.

2019-01-16  Tom Tromey  <tom@tromey.com>

	* objfiles.h (struct minimal_symbol_iterator): Rename.  Move
	earlier.
	(struct objfile) <msymbols_range>: Move from top level.
	<msymbols>: New method.
	(class objfile_msymbols): Remove.
	* symtab.c (default_collect_symbol_completion_matches_break_on):
	Update.
	* symmisc.c (dump_msymbols): Update.
	* stabsread.c (scan_file_globals): Update.
	* objc-lang.c (info_selectors_command, info_classes_command)
	(find_methods): Update.
	* minsyms.c (find_solib_trampoline_target): Update.
	* hppa-tdep.c (hppa_lookup_stub_minimal_symbol): Update.
	* coffread.c (coff_symfile_read): Update.
	* ada-lang.c (ada_lookup_simple_minsym)
	(ada_collect_symbol_completion_matches): Update.