Ticket #3117: Launching editor with CK_Edit shouldn't pass line number.

When pressing F4 to start the editor, a "+1" argument is passed to open
the file at the first line.

For some editor this is absolutely unnecessary since they open the file
there anyways. For some others (at least "joe", but probably others too)
this is harmful: joe has a convenience feature that by default it opens
the file where it was last open, unless of course overridden from
command line. Currently mc forces joe to open the file at the first
line, although opening it where it was last open would be much more
desired.

The right solution would be to consult mc.lib only when opening the
viewer/editor through the "word search in files (M-?)" feature, and
not when F3/F4 is pressed on a file, in the latter case $VIEWER or
$EDITOR should simply be launched with the filename but no additional
parameters.

Initial step: minor refactoring:
(do_edit_at_line): rename to edit_file_at_line.
(edit_file_at_line): changed type of arguments from int to gboolean.
(view_file_at_line): likewise.

Signed-off-by: Andrew Borodin <aborodin@vmail.ru>
Allow launch external editor/viewer w/o line number.

Signed-off-by: Andrew Borodin <aborodin@vmail.ru>
Launching external editor/viewer with F4/F3 w/o passing line number.

Signed-off-by: Andrew Borodin <aborodin@vmail.ru>
Update EN and RU manual pages.

Signed-off-by: Andrew Borodin <aborodin@vmail.ru>
Merge branch '3117_external_editor_line_number'

* 3117_external_editor_line_number:
  Update EN and RU manual pages.
  Launching external editor/viewer with F4/F3 w/o passing line number.
  Allow launch external editor/viewer w/o line number.
  Ticket #3117: Launching editor with CK_Edit shouldn't pass line number.