Merge branch '2206_jump_line'

Merge branch '2206_jump_line'

* 2206_jump_line:
  Add description of feature to man/help
  Implementation of getting last editing/viewing position of file.
  Add default options for most popular editors/viewers.
  Add support of reading parameters for external editor/viewer from main config.
  mc_config_get_string(): if default parameter is NULL, then no any config entities will be created
  mc_config_get_string_raw(): if default parameter is NULL, then no any config entities will be created
  Add lib/strutil/replace:str_replace_all() function.
  Add src/execute.c:execute_external_editor_or_viewer() function.
  Add function lib/utilunix.c:my_systemv_flags()
  Code refactoring: split src/execute.c:execute_with_vfs_arg() function.
  Add tests for src/execute.c:execute_with_vfs_arg() function.
  Add new functions:
  Code refactoring: my_system was split by few functions.
  Add tests for lib/utilunix.c:my_system() function
  Ticket #2206: Add jump support to target line in some external editors