Add checkbox to search only directory names

When the checkbox is checked, only directories are matched against
"Filename" field. Files are not matched and no file is searched for
content even if the field "Content" is not empty.

This is an example feature implemented for open source programming course
at Czech Technical University. It is intentionally based on older version,
so that students can learn how to use git to resolve merge conflicts or
update (rebase) their patches.

Signed-off-by: Michal Sojka <sojkam1@fel.cvut.cz>
Document "Only directories" checkbox
Ticket #3177: fix long start of mc if SHELL is zsh.

Signed-off-by: Andrew Borodin <aborodin@vmail.ru>
Merge branch '3177_zsh_long_start'

* 3177_zsh_long_start:
  Ticket #3177: fix long start of mc if SHELL is zsh.
Ticket #2983: fish VFS: fix handling of filenames with '%'.

Signed-off-by: Andrew Borodin <aborodin@vmail.ru>
Merge branch '2983_fish_filename_percent'

* 2983_fish_filename_percent:
  Ticket #2983: fish VFS: fix handling of filenames with '%'.
Ticket #3183: diffviewer line drawing fix.

The "topmiddle" and "bottommiddle" characters are defined incorrectly
in many skins. This is because the correct definition wouldn't work
with S-Lang build. The only place these characters are used is the
diffviewer if either the +/- signs or the line numbers are shown,
enabled by pressing S or L. The correct definition of these characters
currently show up as 'v' and 'w' characters.

The fix makes the diffviewer use tty_print_alt_char() as it is being used
in other parts of the code, and hence it fixes the bug.
It also fixes the skin definitions.

Signed-off-by: Andrew Borodin <aborodin@vmail.ru>
Merge branch '3183_diffviewer_lines'

* 3183_diffviewer_lines:
  Ticket #3183: diffviewer line drawing fix.
Ticket #3184: minor skin cleanups.

  * Consistent indentation: All skins use now 4 spaces (the default of
mcedit). This makes it easier to copy-paste sections from one skin to
another, while maintaining consistency.
  * Spaces around the '=' sign. The version with spaces is more
readable, especially around double line characters.
  * Make the order of the sections consistent across all skins.
  * In [menu], swap the order of "menusel" and "menuhot" to make the
order consistent with the [dialog] and [error] sections.
  * Add the missing "helptitle" to sand256 skin. This is the only
functional change.

Signed-off-by: Andrew Borodin <aborodin@vmail.ru>
Ticket #3180: remove DFF_FOLDER_COLOR. It's unused.

Signed-off-by: Andrew Borodin <aborodin@vmail.ru>
Ticket #3179: do not consider "String not found" mwssage as error.

If some string isn't found it is a normal situation, not en error.
So show "String not found" message as normal dialog not as error one.

Signed-off-by: Andrew Borodin <aborodin@vmail.ru>
Merge branch '3179_not_found_dialog_uniq'

* 3179_not_found_dialog_uniq:
  Ticket #3179: do not consider "String not found" mwssage as error.
Ticket #3122: xorriso iso9660 show only one depth

Signed-off-by: Slava Zanko <slavazanko@gmail.com>
Merge branch '3122_xorriso_one_depth'

* 3122_xorriso_one_depth:
  Ticket #3122: xorriso iso9660 show only one depth
Merge remote-tracking branch 'osp/only-directories' into homework

Conflicts:
	src/filemanager/find.c
Merge remote-tracking branch 'origin/master' into homework