DECC$FILENAME_ENCODING_UTF8

   C RTL routines that deal with filenames now support filenames in
   UTF-8 encoding when given in UNIX style.

   For example, on an ODS-5 disk the OpenVMS DIRECTORY command
   supports a filename with the following characters:

   disk:[mydir]^U65E5^U672C^U8A9E.txt

   This filename contains three UCS-2 characters (call them xxx,
   yyy, and zzz for typographical purposes) meaning "day", "origin",
   and "language", respectively.

   With UTF-8 support enabled, a C program can now read the filename
   from the VMS directory and use that filename as an UTF-8 encoded
   string.

   For example, opendir("/disk/mydir") followed by a readdir will
   place the following into the d_name field of the supplied dirent
   structure:

   "\xE6\x97\xA5\xE6\x9C\xAC\xE8\xAA\x9E.txt"

   One of the following calls can then open this file:

   open("/disk/mydir/\xE6\x97\xA5\xE6\x9C\xAC\xE8\xAA\x9E.txt",O_RDWR,0)
   open("/disk/mydir/xxxyyyzzz.txt", O_RDWR,0)

   The "\xE6\x97\xA5" above is the byte stream E697A5, which
   represents the xxx character in UTF-8 encoding. 

   This feature enhances the UNIX portability of international
   software that uses UTF-8 encoded filenames.

   The DECC$FILENAME_ENCODING_UTF8 feature logical controls whether
   or not the C RTL allows and correctly interprets Unicode UTF-8
   encoding for filenames given in UNIX style.

   This logical is undefined by default, and the C RTL behavior is
   to accept filenames as ASCII and Latin-1 format.

   This feature works only on ODS-5 disks. Therefore, to enable
   Unicode UTF-8 encoding, you must define both the DECC$FILENAME_
   ENCODING_UTF8 and DECC$EFS_CHARSET logicals to ENABLE.