making cache manager presence/registration optional

I'd like to make the cachemgrRegister calls in various of our fooInit()
calls not require dragging in the whole squid to the binary, this is
part of the blow-out on linked in objects for squid.

Secondly, I'd like to remove the idea of the cachemanager being a global
object and make it be explicitly passed in when it exists.

We discussed this somewhat on irc.

Some possibilities:

Assuming we have a CacheManager class with 'register' and 'unregister'
virtual methods, we could:

* add that as a parameter to the Init calls where this is desirable.
* Have a separate call from Init in modules which asks the module to
register all its menu items with a supplied CacheManager.

I prefer the second option, as it makes the behaviour of init more
occupied with 'what is required to use a module' rather than 'do
everything that /squid/ needs done before running that is related to
this module.' Henrik is concerned that this will increase the
maintenance cost of main(), which is possibly true, but I think we can
address that in future if needed, i.e. by a registry of the modules with
a few functions like 'init', 'registerWithCacheManger' etc.

Thoughts?

Rob

-- 
GPG key available at: <http://www.robertcollins.net/keys.txt>.