Tweak debian devbuilds

See merge request lyskom-elisp-client/lyskom-elisp-client!3

* lyskom-rest.el (lyskom-format-image): Link to jskom when an
  image cannot be displayed.
* swedish-strings.el, english-strings.el (image-no-show): Now
  takes two additional arguments (two links to display).

In emacs-26 duplicate &optional is an error.

  ...
  lyskom.el:42124:26:Error: Duplicate &optional
  make: *** [Makefile:195: lyskom.elc] Error 1

The debian source format i specified three years ago doesn't permit
version suffixes (at least now).

The function generates a warning in emacs-25

 lyskom.el:31094:6:Warning: ‘nil’ is not a condition name (in condition-case)

Since it's not used, just remove it instead of trying to fix it.

Don't redefine kbd if existing definition is correct.

Terminate keep-alive in kill-buffer-hook

Since lyskom-keep-alive-timers is a buffer-local variable,
lyskom-keep-alive-callback can't stop the keep-alive timer
if the buffer has been killed.  As a result, it keeps saying ERROR! in
the mini buffer.

On an idea from Christer Ekholm, terminate the timer explicitly with a
kill-buffer-hook instead.  The error logging in
lyskom-keep-alive-callback has been improved too, to provide more
information on what went wrong if there are other error situations in
the future.

See merge request !2

Since lyskom-keep-alive-timers is a buffer-local variable,
lyskom-keep-alive-callback can't stop the keep-alive timer
if the buffer has been killed.  As a result, it keeps saying ERROR! in
the mini buffer.

On an idea from Christer Ekholm, terminate the timer explicitly with a
kill-buffer-hook instead.  The error logging in
lyskom-keep-alive-callback has been improved too, to provide more
information on what went wrong if there are other error situations in
the future.

To avoid failure when copying the write-protected files.

If HEAD is not a tagged commit then construct lyskom-clientversion the
same way as wen building default target (lyskom.elc)

Commit 8ae3ab53 removed target fast. But I forgot to also remove the
comment telling about it.

Also chmod 444 some more generated files. The reason to write-protect
generated files is to make it harder to accidentally edit them by
mistake.

There is no need to. And if it's writable we don't need to have rm -f
too.

By removing "$(MAKE) $(VERSION-EL)" from the recipe for lyskom.el, and
adding the elisp source-files as dependencies for version.el

make fast doesn't work any more. So instead of trying to fix it, just
remove it.

dont-compile is marked as obsolete in emacs-24.4, and gives a lot of
warnings "Warning: `dont-compile' is an obsolete macro (as of 24.4)."

* lyskom-rest.el (lyskom-do-format): Don't (set-buffer lyskom-buffer)
unless kom-deferred-printing is t. It's not needed then, and
kom-edit-show-commented sets it to nil when inserting the commented
text in *Commented*

Bug introduced in a4b10328.

* elib-string.el (string-replace-match): Track the renamed variables
  elib-string and elib-newtext.
  (elib-string-expand-newtext): Fixed the documentation now that the
    variables are renamed.

The code is supposed to use set-face-strikethru-p if available (in
xemacs). But the function was misspelled in the test, thus never used.

Moved selection of wday from convdate to a more natural place, and
reduced line-length.

The "(decode-time (encode-time" combination must not be used unless
kom-show-mx-date-as-local and must be used on "safe" values, not
directly on the result from parse-time-string.

* view-text.el (lyskom-mx-date-to-time): Removed the use of
calendar-iso-from-absolute and calendar-absolute-from-gregorian from
calendar. Use instead decode-time and encode-time to complete the
result from parse-time-string to include weekday.

The content currently needs to be latin1 or else the help system
displays strings with åäö badly. The setting is done here so that we
don't depend on the environment when building.

To get rid of the following warning when building.

 Warning (emacs): File contents detected as iso-latin-1.
   Consider adding an xml declaration with the encoding specified,
   or saving as utf-8, as mandated by the xml specification.

Handle prefix-argument the way the doc-string says.