Reduce cppcheck warnings (style) in lib subdirectory.

Signed-off-by: Slava Zanko <slavazanko@gmail.com>
Rename structures:

* FileOpContext -> file_op_context_t
* FileOpContextUI -> file_op_context_ui_t

Signed-off-by: Slava Zanko <slavazanko@gmail.com>
Use UTF8_CHAR_LEN instead of a magic number

Signed-off-by: Slava Zanko <slavazanko@gmail.com>
Clarify usage of WPanel widget.

Signed-off-by: Andrew Borodin <aborodin@vmail.ru>
Reduce cppcheck warnings (style) in src subdirectory.

Signed-off-by: Slava Zanko <slavazanko@gmail.com>