old-filespec
    OpenVMS usage:char_string
    type:         character string
    access:       read only
    mechanism:    by descriptor
    File specification to be trimmed. The old-filespec argument
    contains the address of a descriptor pointing to this file
    specification string.
    The file specification should be an RMS resultant name string.
 new-filespec
    OpenVMS usage:char_string
    type:         character string
    access:       write only
    mechanism:    by descriptor
    Trimmed file specification. The new-filespec argument contains
    the address of a descriptor pointing to this trimmed file
    specification string. LIB$TRIM_FILESPEC writes the trimmed file
    specification into new-filespec.
 word-integer-width
    OpenVMS usage:word_unsigned
    type:         word (unsigned)
    access:       read only
    mechanism:    by reference
    Maximum field width desired. The word-integer-width argument is
    the address of an unsigned word that contains this maximum field
    width.
    If omitted, the current length of new-filespec is used. If new-
    filespec is not a fixed-length string, you should specify word-
    integer-width to ensure that the desired width is used.
 resultant-length
    OpenVMS usage:word_unsigned
    type:         word (unsigned)
    access:       write only
    mechanism:    by reference
    Length of the trimmed file specification, not including any blank
    padding or truncated characters. The resultant-length argument is
    the address of an unsigned word that contains this length. This
    is an optional argument.