variable url-automatic-caching defined but not used

[Klaus Straubinger]

The file url/url-vars.el defines the variable url-automatic-caching,
but it is not used in the whole URL package anywhere. What is worse,
the current behaviour (i.e., caching always) does not correspond to
the default nil setting of this variable.

The function url-store-in-cache in url-cache.el seems a good place to
implement the intended functionality.

Regards
Klaus Straubinger