Don't set auto_name_dirs because it messes up prompts

From http://zsh.sourceforge.net/Doc/Release/Options.html#Completion-4

> AUTO_NAME_DIRS
> Any parameter that is set to the absolute name of a directory immediately
> becomes a name for that directory, that will be used by the ‘%~’ and
> related prompt sequences, and will be available when completion is performed
> on a word starting with ‘~’.
> (Otherwise, the parameter must be used in the form ‘~param’ first.)

Explained in more detail in
https://github.com/wayneeseguin/rvm/issues/3091#issuecomment-60083194

Related issues:
https://github.com/robbyrussell/oh-my-zsh/issues/2857
https://github.com/robbyrussell/oh-my-zsh/issues/3238
https://github.com/wayneeseguin/rvm/issues/3091
Merge pull request #3252 from mcornella/fix-auto-named-dirs-prompt

Don't set auto_name_dirs because it messes up prompts
Force ssh-agent output to use bourne-style syntax

On systems where the shell cannot be changed because of a strict
security policy, ssh-agent will use the syntax of whatever the
default $SHELL is.
For instance, if the default shell is tcsh, ssh-agent will use the
c-shell style (setenv).

This change forces ssh-agent to use bourne-style syntax since that
has to be later interpreted by zsh. Consequently, the environment
file will contain `export' statements from now on (instead of
`setenv').