Make Lisp_Save_Value more versatile storage for up to four objects.
* lisp.h (toplevel): Enumeration to describe types of saved objects.
(struct Lisp_Save_Value): New layout.  Adjust comments.
(XSAVE_POINTER): New macro.
(XSAVE_INTEGER): Likewise.
(allocate_misc): Add prototype.
(free_misc): Likewise.
* alloc.c (allocate_misc): Now global.
(free_misc): Likewise.  Adjust comment.
(make_save_value): Use new Lisp_Save_Value layout.  Adjust comment.
(free_save_value): Likewise.
(mark_object): Likewise.
* editfns.c (save_excursion_save): Pack everything within
Lisp_Save_Value and so avoid xmalloc.
(save_excursion_restore): Adjust to match new layout.  Use free_misc
because we do not allocate extra memory any more.  Add eassert.
* print.c (print_object): New code to print Lisp_Save_Value.  Do not
rely on valid_lisp_object_p if !GC_MARK_STACK.  Adjust comments.
* dired.c, fileio.c, font.c, ftfont.c, gtkutil.c, keymap.c,
* lread.c, nsmenu.m, nsterm.h, xfns.c, xmenu.c, xselect.c:
Use XSAVE_POINTER and XSAVE_INTEGER where appropriate.
Fix compilation with GC_MARK_STACK == GC_USE_GCPROS_AS_BEFORE.
* eval.c (eval_sub): Protect `form' from being GCed before its
car and cdr becomes protected with the backtrace entry.
* lisp.h (toplevel): Fix typo in comment.
Auto-commit of loaddefs files.
Sync window-point and point in calendar-redraw
Avoid needless casts with XSAVE_POINTER.

* alloc.c (mark_object) [GC_MARK_STACK]:
* dired.c (directory_files_internal_unwind):
* fileio.c (do_auto_save_unwind):
* gtkutil.c (pop_down_dialog):
* keymap.c (map_keymap_char_table_item):
* lread.c (load_unwind):
* nsmenu.m (pop_down_menu):
* print.c (print_object) [GC_MARK_STACK]:
* xfns.c (clean_up_file_dialog):
* xmenu.c (cleanup_widget_value_tree):
Omit casts between XSAVE_POINTER and a pointer type.