By default, `typeset` defines variables locally unless in the main scope.
This is specially bad when using `omz plugin load`, which happens inside
a function, so the declared variables don't continue being defined when
the function finishes and the main scope reappears.

Fixes fb86ec77

Made it work with UTF-8 Console.
Thanks goes to http://blog.ganneff.de/blog/2013/03/zsh-config---and-prompt.html

I added add-zsh-hook support to the themes that didn't have it already.
This allows the themes to co-exist with plugins and lib/termsupport.