Adjust comments/debug to match C bignum code

* doc/lispintro/emacs-lisp-intro.texi (Digression into C):
Adjust to match current C code.
* lisp/emacs-lisp/ert.el (ert--force-message-log-buffer-truncation):
Simplify.
* src/.gdbinit (Lisp_Object_Printer.to_string): Return
a string that says "make_fixnum", not "make_number".

doc/lispintro/emacs-lisp-intro.texi

@@ -9014,26 +9014,24 @@ Lisp; it is written in C and is one of the primitives of the GNU Emacs
 system.  Since it is very simple, I will digress briefly from Lisp and
 describe it here.
 
-@c GNU Emacs 24  in src/editfns.c
-@c the DEFUN for  delete-and-extract-region
-
 @need 1500
 Like many of the other Emacs primitives,
 @code{delete-and-extract-region} is written as an instance of a C
 macro, a macro being a template for code.  The complete macro looks
 like this:
 
+@c This is a copy of editfns.c's DEFUN for delete-and-extract-region.
 @smallexample
 @group
 DEFUN ("delete-and-extract-region", Fdelete_and_extract_region,
        Sdelete_and_extract_region, 2, 2, 0,
        doc: /* Delete the text between START and END and return it.  */)
-       (Lisp_Object start, Lisp_Object end)
+  (Lisp_Object start, Lisp_Object end)
 @{
   validate_region (&start, &end);
-  if (XINT (start) == XINT (end))
+  if (XFIXNUM (start) == XFIXNUM (end))
     return empty_unibyte_string;
-  return del_range_1 (XINT (start), XINT (end), 1, 1);
+  return del_range_1 (XFIXNUM (start), XFIXNUM (end), 1, 1);
 @}
 @end group
 @end smallexample
@@ -9097,9 +9095,9 @@ consists of the following four lines:
 @smallexample
 @group
 validate_region (&start, &end);
-if (XINT (start) == XINT (end))
+if (XFIXNUM (start) == XFIXNUM (end))
   return empty_unibyte_string;
-return del_range_1 (XINT (start), XINT (end), 1, 1);
+return del_range_1 (XFIXNUM (start), XFIXNUM (end), 1, 1);
 @end group
 @end smallexample
 
@@ -9111,27 +9109,28 @@ then return an empty string.
 The @code{del_range_1} function actually deletes the text.  It is a
 complex function we will not look into.  It updates the buffer and
 does other things.  However, it is worth looking at the two arguments
-passed to @code{del_range_1}.  These are @w{@code{XINT (start)}} and
+passed to @code{del_range_1}.  These are @w{@code{XFIXNUM (start)}} and
-@w{@code{XINT (end)}}.
+@w{@code{XFIXNUM (end)}}.
 
 As far as the C language is concerned, @code{start} and @code{end} are
-two integers that mark the beginning and end of the region to be
+two opaque values that mark the beginning and end of the region to be
-deleted@footnote{More precisely, and requiring more expert knowledge
+deleted.  More precisely, and requiring more expert knowledge
-to understand, the two integers are of type @code{Lisp_Object}, which can
+to understand, the two values are of type @code{Lisp_Object}, which
-also be a C union instead of an integer type.}.
+might be a C pointer, a C integer, or a C @code{struct}; C code
+ordinarily should not care how @code{Lisp_Object} is implemented.
 
-Integer widths depend on the machine, and are typically 32 or 64 bits.
+@code{Lisp_Object} widths depend on the machine, and are typically 32
-A few of the bits are used to specify the type of information; the
+or 64 bits.  A few of the bits are used to specify the type of
-remaining bits are used as content.
+information; the remaining bits are used as content.
 
-@samp{XINT} is a C macro that extracts the relevant number from the
+@samp{XFIXNUM} is a C macro that extracts the relevant integer from the
 longer collection of bits; the type bits are discarded.
 
 @need 800
 The command in @code{delete-and-extract-region} looks like this:
 
 @smallexample
-del_range_1 (XINT (start), XINT (end), 1, 1);
+del_range_1 (XFIXNUM (start), XFIXNUM (end), 1, 1);
 @end smallexample
 
 @noindent

lisp/emacs-lisp/ert.el

@@ -792,13 +792,13 @@ This mainly sets up debugger-related bindings."
 This can be useful after reducing the value of `message-log-max'."
   (with-current-buffer (messages-buffer)
     ;; This is a reimplementation of this part of message_dolog() in xdisp.c:
-    ;; if (NATNUMP (Vmessage_log_max))
+    ;; if (FIXNATP (Vmessage_log_max))
     ;;   {
     ;;     scan_newline (Z, Z_BYTE, BEG, BEG_BYTE,
-    ;;                   -XFASTINT (Vmessage_log_max) - 1, 0);
+    ;;                   -XFIXNAT (Vmessage_log_max) - 1, false);
-    ;;     del_range_both (BEG, BEG_BYTE, PT, PT_BYTE, 0);
+    ;;     del_range_both (BEG, BEG_BYTE, PT, PT_BYTE, false);
     ;;   }
-    (when (and (integerp message-log-max) (>= message-log-max 0))
+    (when (natnump message-log-max)
       (let ((begin (point-min))
             (end (save-excursion
                    (goto-char (point-max))

src/.gdbinit

@@ -1316,7 +1316,7 @@ if hasattr(gdb, 'printing'):
       itype = ival >> (0 if USE_LSB_TAG else VALBITS)
       itype = itype & ((1 << GCTYPEBITS) - 1)
 
-      # For a Lisp integer N, yield "make_number(N)".
+      # For a Lisp fixnum N, yield "make_fixnum(N)".
       if itype == Lisp_Int0 or itype == Lisp_Int1:
         if USE_LSB_TAG:
           ival = ival >> (GCTYPEBITS - 1)
@@ -1324,7 +1324,7 @@ if hasattr(gdb, 'printing'):
           ival = ival | (-1 << VALBITS)
         else:
           ival = ival & ((1 << VALBITS) - 1)
-        return "make_number(%d)" % ival
+        return "make_fixnum(%d)" % ival
 
       # For non-integers other than nil yield "XIL(N)", where N is a C integer.
       # This helps humans distinguish Lisp_Object values from ordinary