FIXFOR: Ticket #2206: Add jump support to target line in some external editors
FIXFOR: Code refactoring: my_system was split by few functions.
FIXFOR: Add new functions:
FIXFOR: Add function lib/utilunix.c:my_systemv_flags()
FIXFOR: Add src/execute.c:execute_external_editor_or_viewer() function.
FIXFOR: Add lib/strutil/replace:str_replace_all() function.
FIXFOR: Add support of reading parameters for external editor/viewer from main config.
FIXFOR: Implementation of getting last editing/viewing position of file.
FIXFOR: Add description of feature to man/help
FIXFOR: Add tests for lib/utilunix.c:my_system() function