Remove some Emacs 19 compat code and references

* lisp/progmodes/sql.el:
* lisp/mh-e/mh-show.el (mh-display-msg): Remove Emacs 19 compat code.
* lisp/emacs-lisp/edebug.el (edebug-mark-marker): Make into
obsolete alias for mark-marker.
(edebug--display-1, edebug-bounce-point)
(edebug-outside-excursion): Adjust callers.
* lisp/net/snmp-mode.el:
* lisp/forms.el: Remove references to Emacs 19.
(forms-use-text-properties): Doc fix.

lisp/progmodes/sql.el

@@ -232,9 +232,6 @@
 
 (require 'cl-lib)
 (require 'comint)
-;; Need the following to allow GNU Emacs 19 to compile the file.
-(eval-when-compile
-  (require 'regexp-opt))
 (require 'custom)
 (require 'thingatpt)
 (require 'view)