Calculate pauses in file operations.

  * (file_op_context_t): new 'pauses' member.
  * (file_error): pass file operation context to calculate pause.
  * (real_warn_same_file): likewise.
  * (real_do_file_error): likewise.
  * (real_query_recursive): calculate pause.
  * (overwrite_query_dialog): likewise.
  * (calc_copy_file_progress): calculate use ctx->pauses to calculate ETA.
  * (warn_same_file):
  * (check_same_file):
  * (check_hardlinks):
  * (make_symlink):
  * (do_file_error):
  * (files_error):
  * (try_remove_file):
  * (move_file_file):
  * (try_erase_dir):
  * (do_move_dir_dir):
  * (copy_file_file):
  * (copy_dir_dir):
  * (panel_operate):
  * (tree_move): related changes.

Signed-off-by: Andrew Borodin <[email protected]>