docs: document zsh special array $options.

[Ralf Wildenhues]

<http://thread.gmane.org/gmane.comp.gnu.libtool.patches/10643>

Quoting zshall(1):

THE ZSH/PARAMETER MODULE
       The  zsh/parameter  module  gives  access  to some of the internal hash
       tables used by the shell by defining some special parameters.

       options
              The keys for this associative array are the names of the options
              that  can  be  set  and  unset  using  the  setopt  and unsetopt
              builtins. The value of each key is either the string on  if  the
              option  is  currently  set,  or  the string off if the option is
              unset.  Setting a key to one of these strings is like setting or
              unsetting  the  option,  respectively.  Unsetting  a key in this
              array is like setting it to the value off.

This lives even after 'emulate sh'.  OK to commit?

Thanks,
Ralf

    docs: document zsh special array $options.
    
    * doc/autoconf.texi (Special Shell Variables): Add entry for
    `options'.

diff --git a/doc/autoconf.texi b/doc/autoconf.texi
index d3774c0..e8d65cb 100644
--- a/doc/autoconf.texi
+++ b/doc/autoconf.texi
@@ -16432,6 +16432,11 @@ Special Shell Variables
 and forget to set @env{NULLCMD},
 your script might be suspended waiting for data on its standard input.
 
address@hidden options
address@hidden options
+For @command{zsh} 4.3.10, @env{options} is treated as an associative
+array even after @code{emulate sh}, so it should not be used.
+
 @item PATH_SEPARATOR
 @evindex PATH_SEPARATOR
 On DJGPP systems, the @env{PATH_SEPARATOR} environment