Simplify mark_object for pseudovectors

Suggested by Pip Cet (Bug#32405#14).
* src/alloc.c (mark_object): Remove unnecessary special cases for
PVEC_MARKER, PVEC_BOOL_VECTOR, PVEC_MISC_PTR, PVEC_USER_PTR, and
PVEC_FINALIZER.

change is to free up an enum Lisp_Type tag value, a scarce

src/alloc.c

@@ -6495,28 +6495,10 @@ mark_object (Lisp_Object arg)
 	    mark_char_table (ptr, (enum pvec_type) pvectype);
 	    break;
 
-	  case PVEC_MARKER:
-	    /* DO NOT mark thru the marker's chain.
-	       The buffer's markers chain does not preserve markers from gc;
-	       instead, markers are removed from the chain when freed by gc.  */
-	  case PVEC_BOOL_VECTOR:
-	  case PVEC_MISC_PTR:
-#ifdef HAVE_MODULES
-	  case PVEC_USER_PTR:
-#endif
-	    /* No Lisp_Objects to mark in these.  */
-	    VECTOR_MARK (ptr);
-	    break;
-
 	  case PVEC_OVERLAY:
 	    mark_overlay (XOVERLAY (obj));
 	    break;
 
-	  case PVEC_FINALIZER:
-	    VECTOR_MARK (ptr);
-	    mark_object (XFINALIZER (obj)->function);
-	    break;
-
 	  case PVEC_SUBR:
 	    break;
 
@@ -6524,6 +6506,8 @@ mark_object (Lisp_Object arg)
 	    emacs_abort ();
 
 	  default:
+	    /* A regular vector, or a pseudovector needing no special
+	       treatment.  */
 	    mark_vectorlike (ptr);
 	  }
       }

src/lisp.h

@@ -2264,7 +2264,9 @@ struct Lisp_Marker
      does not point anywhere.  */
 
   /* For markers that point somewhere,
-     this is used to chain of all the markers in a given buffer.  */
+     this is used to chain of all the markers in a given buffer.
+     The chain does not preserve markers from garbage collection;
+     instead, markers are removed from the chain when freed by GC.  */
   /* We could remove it and use an array in buffer_text instead.
      That would also allow us to preserve it ordered.  */
   struct Lisp_Marker *next;