Finalizer documentation, minor improvements

* doc/lispref/objects.texi (Finalizer Type): New section
(Type Predicates): Mention finalizers in `type-of' documentation.
* doc/lispref/elisp.texi (Top): Link to finalizer type.

* src/data.c (Ftype_of): Make `type-of' work with finalizers.
(syms_of_data): Register Qfinalizer.

* src/print.c (print_object): Print whether a finalizer has
been called.

* test/automated/finalizer-tests.el (finalizer-object-type): Test that
`type-of' works correctly for finalizers.

1 files changed, 4 insertions, 1 deletions

diff --git a/src/print.c b/src/print.c
index d391fd5f7a3..838d03666d4 100644
--- a/src/print.c
+++ b/src/print.c
@@ -2046,7 +2046,10 @@ print_object (Lisp_Object obj, Lisp_Object printcharfun, bool escapeflag)
           break;
 
         case Lisp_Misc_Finalizer:
-          strout ("#<finalizer>", -1, -1, printcharfun);
+          strout ("#<finalizer", -1, -1, printcharfun);
+          if (NILP (XFINALIZER (obj)->function))
+            strout (" used", -1, -1, printcharfun);
+          strout (">", -1, -1, printcharfun);
           break;
 
           /* Remaining cases shouldn't happen in normal usage, but let's