Merge branch '3693_cleanup'

Merge branch '3693_cleanup'

* 3693_cleanup: (31 commits)
  Update po/*.po files.
  src/filemanager/mountlist.c: clarify comments.
  (mc_search_run): document the return value.
  NULL-ize some variables to make unit tests happy.
  Use g_assert() instead of assert(3).
  doc/NEWS: cosmetics.
  Ticket #3703: fix potential NULL dereference.
  Sync with gnulib 5159ac54e0c73df4432a681e2e267df4ffcc04e4.
  MSG_INIT is handled by default.
  Clarify startup.
  (panel_callback) [MSG_FOCUS]: don't redraw panel here.
  (setup_panels): fix location of right panel.
  Add -Wformat-signedness option.
  (my_systemv): cleanup unreachable-code warning.
  (vfs_die): cleanup no attribute noreturn warning.
  (my_exit): cleanup no attribute noreturn warning.
  (edit_move_block_to_left): reduce variable scope.
  (edit_move_block_to_left): cleanup -Wunsafe-loop-optimizations.
  lib/serialize.c: cleanup -Wformat-signedness warning.
  (vfs_path_deserialize): refactoring.
  ...