m4 1.4.8 manual about --prepend-include is outdated

Hi,

See below for the outdated document. Since -B is discouraged, it may
be better to be documented. Thanks.

$ info m4 | grep 'GNU M4 (version'
This manual (31 December 2016) is for GNU M4 (version 1.4.18), a package
$ info m4 | grep prepend-include -A 3
   If the '--prepend-include' or '-B' command-line option was provided
(*note Invoking m4: Preprocessor features.), those directories are
searched first, in reverse order that those options were listed on the
command line.  Then 'm4' looks in the current working directory.  Next
$ m4 --version
m4 (GNU M4) 1.4.18
Copyright (C) 2016 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>.
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

Written by Rene' Seindal.
$ m4 -B . < /dev/null
m4: warning: `m4 -B' may be removed in a future release

-- 
Regards,
Peng