Remove some references to Emacs 18 and 19

* doc/misc/forms.texi (Modifying Forms Contents, Error Messages):
* lisp/arc-mode.el:
* lisp/emacs-lisp/edebug.el (edebug-temp-display-freq-count):
* lisp/type-break.el: Remove some references to Emacs 18 and 19.

doc/misc/forms.texi

@@ -658,15 +658,6 @@ displayed record.  You cannot delete or modify the fixed, explanatory
 text that comes from string formatting elements, but you can modify the
 actual field contents.
 
-@ignore
-@c This is for the Emacs 18 version only.
-If the contents of the forms cannot be recognized properly, this is
-signaled using a descriptive text.  @xref{Error Messages}, for more info.
-The cursor will indicate the last part of the forms which was
-successfully parsed.  It's important to avoid entering field contents
-that would cause confusion with the field-separating fixed text.
-@end ignore
-
 If the variable @code{forms-modified-record-filter} is non-@code{nil},
 it is called as a function before the new data is written to the data
 file.  The function receives one argument, a vector that contains the
@@ -795,23 +786,6 @@ The first element of a list which is an element of
 A list element was supplied in @code{forms-format-list} which was not a
 string, number or list.
 
-@ignore
-@c This applies to Emacs 18 only.
-@c Error messages generated while a modified form is being analyzed.
-
-@item Parse error: not looking at `...'
-When re-parsing the contents of a forms, the text shown could not
-be found.
-
-@item Parse error: cannot find `...'
-When re-parsing the contents of a forms, the text shown, which
-separates two fields, could not be found.
-
-@item Parse error: cannot parse adjacent fields @var{xx} and @var{yy}
-Fields @var{xx} and @var{yy} were not separated by text, so could not be
-parsed again.
-@end ignore
-
 @item Warning: this record has @var{xx} fields instead of @var{yy}
 The number of fields in this record in the data file did not match
 @code{forms-number-of-fields}.  Missing fields will be made empty.

lisp/arc-mode.el

@@ -41,8 +41,7 @@
 ;;                changes will first take effect when the archive buffer
 ;;                is saved.  You will be warned about this.
 ;;
-;; * dos-fns.el:  (Part of Emacs 19).  You get automatic ^M^J <--> ^J
+;; * dos-fns.el:  You get automatic ^M^J <--> ^J conversion.
-;;                conversion.
 ;;
 ;; arc-mode.el does not work well with crypt++.el; for the archives as
 ;; such this could be fixed (but wouldn't be useful) by declaring such

lisp/emacs-lisp/edebug.el

@@ -4461,7 +4461,6 @@ reinstrument it."
 (defun edebug-temp-display-freq-count ()
   "Temporarily display the frequency count data for the current definition.
 It is removed when you hit any char."
-  ;; This seems not to work with Emacs 18.59. It undoes too far.
   (interactive)
   (let ((inhibit-read-only t))
     (undo-boundary)

lisp/type-break.el

@@ -51,8 +51,6 @@
 ;; this, but I think the health of my hands is far more important than a
 ;; few pages of virtual memory.
 
-;; This program has no hope of working in Emacs 18.
-
 ;; This package was inspired by Roland McGrath's hanoi-break.el.
 ;; Several people contributed feedback and ideas, including
 ;;      Roland McGrath <roland@gnu.org>