Support MS-Windows file names that use characters outside of ANSI codepage.

Support MS-Windows file names that use characters outside of ANSI codepage.

 src/w32.c (get_file_security, set_file_security)
 (create_symbolic_link): Separate pointers and boolean flags for
 ANSI and Unicode APIs.  Use the latter if w32_unicode_filenames is
 non-zero, else the former.
 (codepage_for_filenames, filename_to_utf16, )
 (filename_from_utf16, filename_to_ansi, filename_from_ansi): New
 functions.
 (init_user_info): Allow $HOME and $SHELL to include non-ANSI
 characters.
 (normalize_filename): Lose the DBCS code, now works on UTF-8.
 Accept only one argument; all callers changed.
 (dostounix_filename): Remove the second argument, now works in
 UTF-8.  All callers changed.
 (parse_root): Lose DBCS code.
 (get_long_basename, w32_get_short_filename, init_environment)
 (GetCachedVolumeInformation, sys_readdir, open_unc_volume)
 (read_unc_volume, logon_network_drive, faccessat, sys_chdir)
 (sys_chmod, sys_creat, sys_fopen, sys_link, sys_mkdir, sys_open)
 (sys_rename_replace, sys_rmdir, sys_unlink, stat_worker, utime)
 (is_symlink, readlink, chase_symlinks, w32_delayed_load): Work in
 Unicode mode if w32_unicode_filenames is non-zero, in ANSI mode
 otherwise.
 (ansi_encode_filename): New function.
 (get_emacs_configuration, get_emacs_configuration_options):
 Functions deleted.
 (add_volume_info, GetCachedVolumeInformation): Run the input file
 name through unixtodos_filename, to ensure it is stored and
 referenced in canonical form.
 (get_volume_info): Lose the DBCS code, now works in UTF-8.
 (logon_network_drive, sys_link, utime): Improve error handling.
 (sys_access): New function.
 (hashval, generate_inode_val): Unused functions deleted.
 (symlink, readlink, readlinkat): Lose DBCS code, now works in UTF-8.
 (check_windows_init_file): Convert error message from UTF-8 to
 ANSI codepage, for display in the message box.
 (globals_of_w32): Set w32_unicode_filenames according to the OS
 version.
 src/w32term.c (construct_drag_n_drop): Work in Unicode mode when
 w32_unicode_filenames is non-zero, ANSI mode otherwise.
 (syms_of_w32term): Declare w32-unicode-filenames.
 src/w32proc.c (new_child, delete_child): Remove code that handled
 unused pending_deletion and input_file members of the child struct.
 (create_child, sys_spawnve): Convert all file names to ANSI
 codepage.  Use ANSI APIs explicitly; forcibly fail if any file
 name cannot be encoded in ANSI codepage.  Don't use
 unixtodos_filename, mirror slashes by hand.
 (record_infile, record_pending_deletion): Functions deleted.
 (Fw32_short_file_name): Call w32_get_short_filename instead of
 GetShortPathName.
 src/w32notify.c (add_watch): Work in Unicode mode when
 w32_unicode_filenames is non-zero, ANSI mode otherwise.
 (Fw32notify_add_watch): Rewrite to avoid using GetFullPathName;
 instead, do the same with Lisp primitives.
 src/w32fns.c (file_dialog_callback, Fx_file_dialog)
 (Fsystem_move_file_to_trash, Fw32_shell_execute)
 (Ffile_system_info, Fdefault_printer_name): Work in Unicode mode
 when w32_unicode_filenames is non-zero, ANSI mode otherwise.
 (Fw32_shell_execute): Improve error reporting.
 (Fdefault_printer_name): Ifdef away for Cygwin.
 src/w32.h (struct _child_process): Remove input_file and
 pending_deletion members that are no longer used.
 (dostounix_filename, w32_get_short_filename, filename_from_ansi)
 (filename_to_ansi, filename_from_utf16, filename_to_utf16)
 (ansi_encode_filename): New and updated prototypes.
 src/unexw32.c (open_input_file, open_output_file, unexec): Use ANSI
 APIs explicitly.
 (unexec): Don't use dostounix_filename, it expects a file name in
 UTF-8.  Instead, mirror backslashes by hand.  Convert NEW_NAME to
 ANSI encoding.
 src/fileio.c (Ffile_name_directory, file_name_as_directory)
 (directory_file_name, Fexpand_file_name)
 (Fsubstitute_in_file_name) [WINDOWSNT]: Adapt to the change in
 arguments of dostounix_filename.
 (Fexpand_file_name) [WINDOWSNT]: Convert value of $HOME to UTF-8.
 use MAX_UTF8_PATH for size of file-name strings.
 (emacs_readlinkat): Build an explicitly unibyte string for file
 names.
 (syms_of_fileio) <file-name-coding-system>
 default-file-name-coding-system>: Mention MS-Windows peculiarities.
 src/emacs.c (init_cmdargs) [WINDOWSNT]: Convert argv[0] to UTF-8.
 (main) [WINDOWSNT]: Convert the argv[] elements that are files or
 directories to UTF-8.
 (decode_env_path) [WINDOWSNT]: Convert file names taken from the
 environment, and each element of the input PATH, to UTF-8.
 src/dired.c (file_attributes): Use build_unibyte_string explicitly
 to make Lisp strings from user and group names.
 src/coding.h (ENCODE_FILE, DECODE_FILE): Just call encode_file and
 decode_file.
 src/coding.c (decode_file_name, encode_file_name): New functions.
 src/termcap.c (tgetent): Adapt to the change in arguments of
 dostounix_filename.
 src/sysdep.c (sys_subshell) [WINDOWSNT]: Use MAX_UTF8_PATH for file
 names.
 src/msdos.c (dostounix_filename, init_environment): Adapt to the
 change in arguments of dostounix_filename.
 src/image.c (xpm_load, tiff_load, gif_load, imagemagick_load)
 [WINDOWSNT]: Encode file names passed to the image libraries in
 ANSI codepage.
 src/gnutls.c (Fgnutls_boot): Encode all file names passed to GnuTLS.
 [WINDOWSNT]: Convert file names to the current ANSI codepage.
 src/filelock.c (lock_file) [WINDOWSNT]: Adapt to the change in
 arguments of dostounix_filename.

 nt/inc/ms-w32.h (MAX_UTF8_PATH): New macro.
 (opendir, closedir, readdir, seekdir): Redirect to replacement
 functions.
 nt/inc/dirent.h: Make d_name[] be MAXNAMELEN*4 characters long.

 lisp/term/w32-win.el (w32-handle-dropped-file):
 lisp/startup.el (normal-top-level):
 lisp/net/browse-url.el (browse-url-file-url):
 lisp/dnd.el (dnd-get-local-file-name): On MS-Windows, encode and
 decode file names using 'utf-8' rather than
 file-name-coding-system.

 doc/emacs/mule.texi (File Name Coding): Document file-name encoding
 peculiarities on MS-Windows.

 doc/lispref/nonascii.texi (Encoding and I/O): Document file-name encoding
 peculiarities on MS-Windows.

 etc/NEWS: Mention support on MS-Windows of file names outside of the
 current locale.

Fixes: debbugs:7100