Remove unused functions from src/libudev/{conf-files,exit-status,hashmap,log,path-util,set,strv}.c

A lot of upstream commits cross many boundaries between systemd code
and udev code.  The point of intersection is upstreams src/shared
folder.  The best way we find to track them is to apply their commits
to udev and libudev and then just pick remove functions from the
shared folder.  Its timely but it gives us the best control over what
gets in and what doesnt.

In this commit we removed the following functions:

  conf_files_list_nulstr
  exit_status_to_string
  is_clean_exit_lsb
  uint64_hash_func
  uint64_compare_func
  hashmap_free_free_free
  hashmap_update
  hashmap_get2
  hashmap_remove_and_replace
  hashmap_remove_value
  hashmap_steal_first_key
  hashmap_next
  log_forget_fds
  log_set_facility
  log_meta_object
  log_struct_internal
  log_set_target_from_string
  log_set_max_level_from_string
  log_get_target
  log_get_max_level
  log_show_color_from_string
  log_show_location_from_string
  log_on_console
  is_path
  path_split_and_make_absolute
  set_ensure_allocated
  set_replace
  set_remove_and_put
  set_size
  set_isempty
  set_iterate_skip
  set_steal_first
  set_first
  set_last
  set_merge
  set_move_one
  set_copy
  set_clear_free
  set_get_strv
  strv_find_prefix
  strv_merge_concat
  strv_split_newlines
  strv_join
  strv_remove_prefix
  strv_parse_nulstr
  strv_overlap
  strv_sort
  strv_print

Signed-off-by: Anthony G. Basile <blueness@gentoo.org>