Ticket #2968: mcviewer: broken Raw/Parse and Format/UnformatRaw/Parse and Format/Unformat

...after CK_FileNext/CK_FilePrev.

Initial commit: refactoring of mcview_t typedef.

Signed-off-by: Andrew Borodin <aborodin@vmail.ru>
(exec_extension_view): refactoring: remove temporary file in exec_extension().

Signed-off-by: Andrew Borodin <aborodin@vmail.ru>
(exec_extension): rename variable.
(regex_command_for): new function to use regex_command in already created viewer/editor

...and related changes.

Signed-off-by: Andrew Borodin <aborodin@vmail.ru>
Fix mode switch after CK_FileNext/CK_FilePrev.

Signed-off-by: Andrew Borodin <aborodin@vmail.ru>
Merge branch '2968_viewer_next_prev_mode'

* 2968_viewer_next_prev_mode:
  Fix mode switch after CK_FileNext/CK_FilePrev.
  (regex_command_for): new function to use regex_command in already created viewer/editor
  (exec_extension): rename variable.
  (exec_extension_view): refactoring: remove temporary file in exec_extension().
  Ticket #2968: mcviewer: broken Raw/Parse and Format/UnformatRaw/Parse and Format/Unformat